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Summary of restructuring activities

The following table summarizes the restructuring and related charges (in thousands):



	Three months ended				Six months ended
	June 29, 2018		June 30, 2017		June 29, 2018		June 30, 2017
Restructuring and related charges in:
Cost of revenue	$	115	$	278	$	877	$	786
Operating expenses - Restructuring and related charges	631		777		1,717		2,056
Total restructuring and related charges	$	746	$	1,055	$	2,594	$	2,842

Harmonic 2016 Restructuring Plan [Member]

Schedule of Restructuring Reserve by Type of Cost

The following table summarizes the activity in the Company’s restructuring accrual related to the Harmonic 2016 Restructuring Plan during the six months ended June 29, 2018 (in thousands):



	Excess facilities			TVN VDP ⁽¹⁾			Total
Balance at December 31, 2017	$	2,426		$	5,128		$	7,554
Adjustments to restructuring provisions	66			477			543
Cash payments	(502		)	(1,653		)	(2,155		)
Foreign exchange gain	—			(107		)	(107		)
Balance at June 29, 2018	1,990			3,845			5,835
Less: current portion ⁽¹⁾	(900		)	(2,446		)	(3,346		)
Long-term portion ⁽¹⁾	$	1,090		$	1,399		$	2,489

Convertible Notes, Other Debts And Capital Leases (Tables)

6 Months Ended

Jun. 29, 2018

Debt Disclosure [Abstract]

Schedule of Carrying Values and Estimated Fair Values of Debt Instruments

The following table presents the components of the Notes as of June 29, 2018 and December 31, 2017 (in thousands, except for years and percentages):



	June 29, 2018			December 31, 2017
Liability:
Principal amount	$	128,250		$	128,250
Less: Debt discount, net of amortization	(14,767		)	(17,404		)
Less: Debt issuance costs, net of amortization	(1,781		)	(2,098		)
Carrying amount	$	111,702		$	108,748
Remaining amortization period (years)	2.4			2.9
Effective interest rate on liability component	9.94		%	9.94		%
Carrying amount of equity component	$	26,062		$	26,062

Convertible Debt Interest

The following table presents interest expense recognized for the Notes (in thousands):



	Three months ended				Six months ended
	June 29, 2018		June 30, 2017		June 29, 2018		June 30, 2017
Contractual interest expense	$	1,282	$	1,282	$	2,565	$	2,565
Amortization of debt discount	1,340		1,214		2,637		2,388
Amortization of debt issuance costs	161		146		317		288
Total interest expense recognized	$	2,783	$	2,642	$	5,519	$	5,241

Schedule of Other Debt and Capital Leases

he Company has a variety of debt and credit facilities in France to satisfy the financing requirements of TVN operations. These arrangements are summarized in the table below (in thousands):



	June 29, 2018			December 31, 2017
Financing from French government agencies related to various government incentive programs ⁽¹⁾	$	14,401		$	20,565
Term loans	1,081			1,282
Obligations under capital leases	559			1,099
Total debt obligations	16,041			22,946
Less: current portion	(1,723		)	(7,610		)
Long-term portion	$	14,318		$	15,336

Schedule of Maturities of Long-term Debt

The table below presents the future minimum repayments of debts and capital lease obligations for TVN as of June 29, 2018 (in thousands):



Years ending December 31,	Capital lease obligations		Other Debt obligations
2018 (remaining six months)	$	395	$	864
2019	92		6,879
2020	49		6,687
2021	23		497
2022	—		457
Thereafter	—		98
Total	$	559	$	15,482

Employee Benefit Plans and Stock-based Compensation (Tables)

6 Months Ended

Jun. 29, 2018

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Summary of Stock Options Outstanding

The following table summarizes the Company’s stock option activities and related information during the six months ended June 29, 2018 (in thousands, except per share amounts and terms):



	Stock Options Outstanding
	Number of Shares		Weighted Average Exercise Price Per Share		Weighted Average Remaining Contractual Term (Years)	Aggregate Intrinsic Value
Balance at December 31, 2017	3,880		$	6.04
Granted	—		—
Exercised	(87	)	2.94
Forfeited	(35	)	4.76
Canceled or expired	(538	)	8.75
Balance at June 29, 2018	3,220		5.69		2.8	$	866.8
As of June 29, 2018
Vested and expected to vest	3,208		5.69		2.8	$	859.3
Exercisable	2,958		5.77		2.7	$	696.1

Summary of Restricted Stock Units Outstanding

The following table summarizes the Company’s RSUs activities and related information during the six months ended June 29, 2018 (in thousands, except per share amounts and terms):



	Restricted Stock Units Outstanding
	Number of Shares		Weighted Average Grant Date Fair Value Per Share
Balance at December 31, 2017	2,904		5.09
Granted	3,293		3.74
Vested	(2,220	)	4.75
Forfeited	(183	)	5.09
Balance at June 29, 2018	3,794		4.12

Schedule of Defined Benefit Plans Obligations

The table below presents the components of net periodic benefit costs (in thousands):



	Three months ended				Six months ended
	June 29, 2018		June 30, 2017		June 29, 2018		June 30, 2017
Service cost	$	63	$	55	$	126	$	110
Interest cost	19		16		38		32
Recognized net actuarial loss	—		2		—		3
Net periodic benefit cost	$	82	$	73	$	164	$	145

Summary of Stock-Based Compensation Expense

Stock-based Compensation

The following table summarizes stock-based compensation for all plans (in thousands):



	Three months ended				Six months ended
	June 29, 2018		June 30, 2017		June 29, 2018		June 30, 2017
Stock-based compensation in:
Cost of revenue	$	448	$	700	$	963	$	1,145
Research and development expense	818		1,337		2,622		2,314
Selling, general and administrative expense	1,746		2,099		5,184		3,928
Total stock-based compensation in operating expense	2,564		3,436		7,806		6,242
Total stock-based compensation	$	3,012	$	4,136	$	8,769	$	7,387

Valuation Assumptions for Stock Options



	Stock Options
	Three and six months ended
	June 30, 2017
Expected term (years)	4.3
Volatility	43%
Risk-free interest rate	1.7%
Expected dividends	0.0%

Schedule of Share-based Payment Award, Employee Stock Purchase Plan, Valuation Assumptions



	ESPP Purchase Period Ending
	July 2, 2018		July 3, 2017
Expected term (years)	0.5		0.5
Volatility	60	%	41	%
Risk-free interest rate	1.7	%	1.0	%
Expected dividends	0.0	%	0.0	%
Estimated weighted average fair value per share at purchase date	$1.34		$1.40

Income Taxes (Tables)

6 Months Ended

Jun. 29, 2018

Income Tax Disclosure [Abstract]

Schedule of income before income tax

The Company reported the following operating results for the periods presented (in thousands):



	Three months ended						Six months ended
	June 29, 2018			June 30, 2017			June 29, 2018			June 30, 2017
Loss before income taxes	$	(2,022	)	$	(30,921	)	$	(14,638	)	$	(55,180	)
Provision for income taxes	891			579			1,969			347
Effective income tax rate	(44.1		)%	(1.9		)%	(13.5		)%	(0.6		)%

Net Loss Per Share (Tables)

6 Months Ended

Jun. 29, 2018

Earnings Per Share [Abstract]

Numerators and Denominators of Basic and Diluted Net Income (Loss) Per Share Computations

The following table sets forth the computation of the basic and diluted net loss per share (in thousands, except per share amounts):



	Three months ended						Six months ended
	June 29, 2018			June 30, 2017			June 29, 2018			June 30, 2017
Numerator:
Net loss	$	(2,913	)	$	(31,500	)	$	(16,607	)	$	(55,527	)
Denominator:
Weighted average number of common shares outstanding
Basic and diluted	85,304			80,590			84,616			80,203
Net loss per share:
Basic and diluted	$	(0.03	)	$	(0.39	)	$	(0.20	)	$	(0.69	)

Anti-dilutive Securities

The following table sets forth the potential weighted common shares outstanding that were excluded from the computation of basic and diluted net loss per share calculations (in thousands):



	Three months ended		Six months ended
	June 29, 2018	June 30, 2017	June 29, 2018	June 30, 2017
Stock options	3,234	4,614	3,469	4,753
RSUs	3,326	3,400	2,766	3,054
Stock purchase rights under the ESPP	541	578	689	385
Warrants ⁽¹⁾	782	782	782	782
Total ⁽²⁾	7,883	9,374	7,706	8,974

Segment Information (Tables)

6 Months Ended

Jun. 29, 2018

Segment Reporting [Abstract]

Segment Reporting Information, by Segment

The following table provides summary financial information by reportable segment (in thousands):



	Three months ended					Six months ended
	June 29, 2018 ⁽¹⁾		June 30, 2017			June 29, 2018			June 30, 2017
Video
Revenue	$	79,208	$	73,379		$	150,956		$	147,721
Gross profit	43,558		37,720			84,784			78,493
Operating income (loss)	6,239		(8,947		)	8,234			(14,783		)
Cable Access
Revenue	$	20,236	$	8,936		$	38,726		$	17,537
Gross profit	10,187		1,699			18,827			3,909
Operating income (loss)	540		(7,411		)	(973		)	(13,491		)
Total
Revenue	$	99,444	$	82,315		$	189,682		$	165,258
Gross profit	53,745		39,419			103,611			82,402
Operating income (loss)	6,779		(16,358		)	7,261			(28,274		)

A reconciliation of the Company’s consolidated segment operating income (loss) to consolidated loss before income taxes is as follows (in thousands):



	Three months ended						Six months ended
	June 29, 2018			June 30, 2017			June 29, 2018			June 30, 2017
Total segment operating income (loss)	$	6,779		$	(16,358	)	$	7,261		$	(28,274	)
Amortization of warrants	(284		)	—			(395		)	—
Unallocated corporate expenses	(746		)	(4,853		)	(2,588		)	(8,775		)
Stock-based compensation	(3,012		)	(4,136		)	(8,769		)	(7,387		)
Amortization of intangibles	(2,095		)	(2,075		)	(4,194		)	(4,144		)
Income (loss) from operations	642			(27,422		)	(8,685		)	(48,580		)
Non-operating expense, net	(2,664		)	(3,499		)	(5,953		)	(6,600		)
Loss before income taxes	$	(2,022	)	$	(30,921	)	$	(14,638	)	$	(55,180	)

Unallocated Corporate Expenses

Commitments and Contingencies (Tables)

6 Months Ended

Jun. 29, 2018

Commitments and Contingencies Disclosure [Abstract]

Future Minimum Lease Payments Under Non-cancelable Operating Leases

Future minimum lease payments under non-cancelable operating leases as of June 29, 2018 are as follows (in thousands):



Years ending December 31,
2018 (remaining six months)	$	6,505
2019	11,420
2020	8,379
2021	2,907
2022	2,431
Thereafter	10,758
Total	$	42,400

Summary of Warranty Accrual Included in Accrued Liabilities

Activity for the Company’s warranty accrual, which is included in “Accrued and other current liabilities”, is summarized below (in thousands):



	Three months ended						Six months ended
	June 29, 2018			June 30, 2017			June 29, 2018			June 30, 2017
Balance at beginning of period	$	4,522		$	4,585		$	4,381		$	4,862
Accrual for current period warranties	1,714			1,277			3,450			2,495
Warranty costs incurred	(1,589		)	(1,720		)	(3,184		)	(3,215		)
Balance at end of period	$	4,647		$	4,142		$	4,647		$	4,142

Recent Accounting Pronouncements - Revenue From Contracts With Customers Beginning Balance Sheet Impact (Details) - USD ($) $ in Thousands	Jun. 29, 2018	Jan. 01, 2018	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable, net	$ 82,635		$ 69,844
Prepaid expenses and other current assets	19,377		18,931
Other long-term assets	42,863		42,913
Deferred revenue	56,278		52,429
Other non-current liabilities	19,169		22,626
Accumulated deficit	(2,062,988)		$ (2,057,812)
Accounting Standards Update 2014-09 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable, net		$ 71,625
Prepaid expenses and other current assets		22,509
Other long-term assets		43,686
Deferred revenue		47,603
Other non-current liabilities		22,153
Accumulated deficit		(2,046,381)
Calculated under Revenue Guidance in Effect before Topic 606 [Member] \| Accounting Standards Update 2014-09 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable, net	78,065
Prepaid expenses and other current assets	15,918
Other long-term assets	42,360
Deferred revenue	60,032
Other non-current liabilities	19,594
Accumulated deficit	(2,075,699)
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] \| Accounting Standards Update 2014-09 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable, net	4,570	1,781
Prepaid expenses and other current assets	3,459	3,578
Other long-term assets	503	773
Deferred revenue	(3,754)	(4,826)
Other non-current liabilities	(425)	(473)
Accumulated deficit	$ 12,711	$ 11,431

Recent Accounting Pronouncements - Revenue From Contracts With Customers, Financial Statement Impact (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 29, 2018	Jun. 30, 2017	Jun. 29, 2018	Jun. 30, 2017	Jan. 01, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total net revenue	$ 99,160	$ 82,315	$ 189,287	$ 165,258
Total cost of revenue	47,557	48,500	90,501	91,035
Gross Profit	51,603	33,815	98,786	74,223
Selling, general and administrative	27,988	32,625	59,151	67,256
Loss from operations	642	(27,422)	(8,685)	(48,580)
Loss before income taxes	(2,022)	(30,921)	(14,638)	(55,180)
Net loss	(2,913)	$ (31,500)	(16,607)	$ (55,527)
Accounts receivable, net	82,635		82,635			$ 69,844
Prepaid expenses and other current assets	19,377		19,377			18,931
Other long-term assets	42,863		42,863			42,913
Deferred revenue	56,278		56,278			52,429
Other non-current liabilities	19,169		19,169			22,626
Accumulated deficit	(2,062,988)		(2,062,988)			$ (2,057,812)
Accounting Standards Update 2014-09 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accounts receivable, net					$ 71,625
Prepaid expenses and other current assets					22,509
Other long-term assets					43,686
Deferred revenue					47,603
Other non-current liabilities					22,153
Accumulated deficit					(2,046,381)
Calculated under Revenue Guidance in Effect before Topic 606 [Member] \| Accounting Standards Update 2014-09 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total net revenue	98,714		188,037
Total cost of revenue	47,316		90,141
Gross Profit	51,398		97,896
Selling, general and administrative	28,570		59,541
Loss from operations	(145)		(9,965)
Loss before income taxes	(2,809)		(15,918)
Net loss	(3,700)		(17,887)
Accounts receivable, net	78,065		78,065
Prepaid expenses and other current assets	15,918		15,918
Other long-term assets	42,360		42,360
Deferred revenue	60,032		60,032
Other non-current liabilities	19,594		19,594
Accumulated deficit	(2,075,699)		(2,075,699)
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] \| Accounting Standards Update 2014-09 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total net revenue	446		1,250
Total cost of revenue	241		360
Gross Profit	205		890
Selling, general and administrative	(582)		(390)
Loss from operations	787		1,280
Loss before income taxes	787		1,280
Net loss	787		1,280
Accounts receivable, net	4,570		4,570		1,781
Prepaid expenses and other current assets	3,459		3,459		3,578
Other long-term assets	503		503		773
Deferred revenue	(3,754)		(3,754)		(4,826)
Other non-current liabilities	(425)		(425)		(473)
Accumulated deficit	$ 12,711		$ 12,711		$ 11,431

Recent Accounting Pronouncements - Narratives (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 29, 2018	Jun. 29, 2018	Jan. 01, 2018	Dec. 31, 2017	Jun. 30, 2017	Dec. 31, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred Revenue, Revenue Recognized	$ 24,100	$ 44,000
Accumulated deficit	(2,062,988)	(2,062,988)		$ (2,057,812)
Net Capitalized Contract Costs	1,800	1,800
Capitalized Contract Cost, Amortization	300	500
Accounting Standards Update 2014-09 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accumulated deficit			$ (2,046,381)
Accounting Standards Update 2014-09 [Member] \| Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accumulated deficit	12,711	12,711	11,431
Accounting Standards Update 2016-18 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Restricted Cash	300	300		$ 1,700	$ 1,900	$ 1,800
Prepaid Expenses and Other Current Assets [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net Capitalized Contract Costs	1,300	1,300
Other Noncurrent Assets [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net Capitalized Contract Costs	$ 500	$ 500
Sales Commission Contract Costs [Member] \| Accounting Standards Update 2014-09 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accumulated deficit			$ 1,400

Investments in Equity Securities (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 29, 2018	Jun. 29, 2018	Oct. 22, 2014	Sep. 02, 2014
Vislink plc [Member]
Schedule of Cost-method Investments [Line Items]
Noncontrolling Interest, Ownership Percentage by Parent				3.30%
Cost Method Investments Original Cost				$ 3.3
Pebble Beach Systems [Member]
Schedule of Cost-method Investments [Line Items]
Gain on Change in Fair Value of Cost Investment	$ 0.2	$ 0.2
Variable Interest Entity, Not Primary Beneficiary [Member] \| EDC [Member]
Schedule of Cost-method Investments [Line Items]
Noncontrolling Interest, Ownership Percentage by Parent			18.40%
Cost Method Investments Original Cost			$ 3.5
Cost-method Investments, Other than Temporary Impairment		$ 0.0

Derivatives and Hedging Activities - Additional Information (Details) $ in Millions	6 Months Ended
	Jun. 29, 2018 USD ($)
Not Designated as Hedging Instrument [Member] \| Forward Contracts [Member]
Derivative [Line Items]
Derivative, Term of Contract	3 months
Israel [Member]
Derivative [Line Items]
Compensating Balance, Amount	$ 1.0

Derivative and Hedging Activities gain losses in Statement of Operations (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 29, 2018	Jun. 30, 2017	Jun. 29, 2018	Jun. 30, 2017
Other Nonoperating Income (Expense) [Member] \| Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Losses recognized in income	$ (1,268)	$ (53)	$ (1,382)	$ (185)

Derivatives and Hedging Activities Notional Amounts (Details) - Foreign Exchange Forward [Member] - Not Designated as Hedging Instrument [Member] - Fair Value Hedging [Member] - USD ($) $ in Thousands	Jun. 29, 2018	Dec. 31, 2017
Long [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative Asset, Notional Amount	$ 24,743	$ 12,875
Short [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative Liability, Notional Amount	$ 1,658	$ 1,509

Derivatives and Hedging Activities Assets Liabilities Balance Sheet Location (Details) - Foreign Exchange Contract [Member] - USD ($) $ in Thousands	Jun. 29, 2018	Dec. 31, 2017
Derivatives, Fair Value [Line Items]
Derivative Asset, Current	$ 14	$ 33
Derivative Liability, Current	298	4
Not Designated as Hedging Instrument [Member] \| Prepaid Expenses and Other Current Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Current	14	33
Not Designated as Hedging Instrument [Member] \| Accrued Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Current	$ 298	$ 4

Derivatives and Hedging Activities Asset and Liability Offset (Details) $ in Thousands	Jun. 29, 2018 USD ($)
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Asset, Gross Amounts of Derivatives	$ 14
Derivative Assets, Gross Amounts of Derivatives Offset in the Condensed Consolidated Balance Sheets	0
Net Amounts of Derivative Assets Presented in the Condensed Consolidated Balance Sheets	14
Derivative Liabilities, Gross Amounts of Derivatives	298
Derivative Liabilities, Gross Amounts of Derivatives Offset in the Condensed Consolidated Balance Sheets	0
Net Amounts of Derivatives Liability Presented in the Condensed Consolidated Balance Sheets	298
Financial Instrument Liability	(14)
Derivative Asset Net Amount	0
Financial Instrument Asset	(14)
Derivative Liability Net Amount	$ 284

Fair Value Measurements - Narratives (Details) - USD ($) $ in Thousands	Jun. 29, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other Debts, Excluding Capital Leases	$ 15,482
Assets, Fair Value Disclosure, Nonrecurring	0
Liabilities, Fair Value Disclosure, Nonrecurring	0
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Convertible Debt, Fair Value Disclosures	133,600	$ 129,900
Other Debts, Excluding Capital Leases	15,500	21,800
TVN [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Postemployment Benefits Liability	$ 3,400	$ 5,100

Fair Value Measurements - Financial Assets and Liabilities Measured at Fair Value Based on Three-Tier Fair Value Hierarchy (Detail) - Fair Value, Measurements, Recurring [Member] - USD ($) $ in Thousands	Jun. 29, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured and recorded at fair value	$ 192	$ 55
Total liabilities measured and recorded at fair value	298	4
Cost-method Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured and recorded at fair value	178
Money market funds [Member] \| Cash equivalents [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured and recorded at fair value		22
Foreign exchange forward contracts [Member] \| Prepaid Expenses and Other Current Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured and recorded at fair value	14	33
Foreign exchange forward contracts [Member] \| Accrued Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total liabilities measured and recorded at fair value	298	4
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured and recorded at fair value	178	22
Total liabilities measured and recorded at fair value	0	0
Level 1 [Member] \| Cost-method Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured and recorded at fair value	178
Level 1 [Member] \| Money market funds [Member] \| Cash equivalents [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured and recorded at fair value		22
Level 1 [Member] \| Foreign exchange forward contracts [Member] \| Accrued Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total liabilities measured and recorded at fair value		0
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured and recorded at fair value	14	33
Total liabilities measured and recorded at fair value	298	4
Level 2 [Member] \| Foreign exchange forward contracts [Member] \| Prepaid Expenses and Other Current Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured and recorded at fair value	14	33
Level 2 [Member] \| Foreign exchange forward contracts [Member] \| Accrued Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total liabilities measured and recorded at fair value	298	4
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured and recorded at fair value	0	0
Total liabilities measured and recorded at fair value	$ 0	0
Level 3 [Member] \| Foreign exchange forward contracts [Member] \| Accrued Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total liabilities measured and recorded at fair value		$ 0

Balance Sheet Components - Accounts Receivable, Net (Details) - USD ($) $ in Thousands	Jun. 29, 2018	Dec. 31, 2017
Receivables [Abstract]
Accounts receivable	$ 86,253	$ 74,475
Less: allowances for doubtful accounts and sales returns	(3,618)	(4,631)
Accounts Receivable, Net, Current	$ 82,635	$ 69,844

Balance Sheet Components - Prepaid Expenses And Other Current Assets (Details) - USD ($)
$ in Thousands

Jun. 29, 2018

Dec. 31, 2017

Jun. 30, 2017

Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]

Deferred cost of revenue

$ 7,688

$ 4,440

Prepaid maintenance, royalty, rent, property taxes and value added tax

3,753

3,867

Contract assets(1)

^[1]

2,704

Capitalized commission

1,293

Restricted cash(2)

274

^[2]

530

^[2]

$ 802

Prepaid Expense and Other Assets, Current

^[3]

103

6,609

Other

3,562

3,485

$ 19,377

$ 18,931

[1]	Contract assets reflect the satisfied performance obligations for which the Company does not yet have an unconditional right to consideration.
[2]	Amounts represent cash collateral security for certain bank guarantees. These restricted funds are invested in bank deposits and cannot be withdrawn from the Company’s accounts without the prior written consent of the applicable secured party.
[3]	The Company’s TVN subsidiary in France (the “TVN French Subsidiary”) participates in the French Crédit d’Impôt Recherche program (the “R&D tax credits”) which allows companies to monetize eligible research expenses. The R&D tax credits can be used to offset against income tax payable to the French government in each of the four years after being incurred, or if not utilized, are recoverable in cash. The amount of R&D tax credits recoverable are subject to audit by the French government. The R&D tax credits receivable at June 29, 2018 were approximately $24.0 million and are expected to be recoverable from 2018 through 2022 with $0.1 million reported as a component of “Prepaid expenses and other current assets” and $23.9 million reported as a component of “Other long-term assets” on the Company’s Condensed Consolidated Balance Sheets.

Balance Sheet Components Additional Information (Details) - USD ($)
$ in Thousands

Jun. 29, 2018

Dec. 31, 2017

Jun. 30, 2017

Restricted Cash for bank guarantee

$ 0

$ 1,203

$ 1,142

R&D tax credits receivable

23,940

22,322

TVN [Member] | Research Tax Credit Carryforward [Member]

^[1]

103

$ 6,609

R&D tax credits receivable

24,000

Prepaid Expenses and Other Current Assets [Member] | TVN [Member] | Research Tax Credit Carryforward [Member]

Other Noncurrent Assets [Member] | TVN [Member] | Research Tax Credit Carryforward [Member]

100

Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]

$ 23,900

[1]

The Company’s TVN subsidiary in France (the “TVN French Subsidiary”) participates in the French Crédit d’Impôt Recherche program (the “R&D tax credits”) which allows companies to monetize eligible research expenses. The R&D tax credits can be used to offset against income tax payable to the French government in each of the four years after being incurred, or if not utilized, are recoverable in cash. The amount of R&D tax credits recoverable are subject to audit by the French government. The R&D tax credits receivable at June 29, 2018 were approximately $24.0 million and are expected to be recoverable from 2018 through 2022 with $0.1 million reported as a component of “Prepaid expenses and other current assets” and $23.9 million reported as a component of “Other long-term assets” on the Company’s Condensed Consolidated Balance Sheets.

Balance Sheet Components - Inventories (Details) - USD ($) $ in Thousands	Jun. 29, 2018	Dec. 31, 2017
Inventory Disclosure [Abstract]
Raw materials	$ 1,973	$ 2,881
Work-in-process	755	933
Finished goods	8,871	10,130
Service-related spares	11,395	12,032
Inventory, Net	$ 22,994	$ 25,976

Balance Sheet Components - Property and Equipment, Net (Details) - USD ($) $ in Thousands	Jun. 29, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 145,133	$ 143,845
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	(119,502)	(114,580)
Property, Plant and Equipment, Net	25,631	29,265
Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	88,129	87,121
Software and Software Development Costs [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	35,527	35,139
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	14,978	15,051
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 6,499	$ 6,534

Balance Sheet Components - Other Long Term Assets (Details) - USD ($)
$ in Thousands

Jun. 29, 2018

Dec. 31, 2017

R&D tax credits receivable

$ 23,940

$ 22,322

Deferred tax assets

9,563

10,462

Equity investment

3,771

3,593

Others(1)

^[1]

5,589

6,536

Other Assets, Noncurrent

$ 42,863

$ 42,913

[1]

As of December 31, 2017, the Company had approximately $1.2 million of restricted cash for the bank guarantee associated with the TVN French Subsidiary’s office building lease. The restriction was subsequently released and accordingly, the amount was reclassified to “Cash and cash equivalents” in the six months ended June 29, 2018.

Balance Sheet Components - Accrued and Other Current Liabilities (Details) - USD ($)
$ in Thousands

Jun. 29, 2018

Dec. 31, 2017

Payables and Accruals [Abstract]

Accrued employee compensation and related expenses

$ 15,750

$ 16,414

Customer deposits

4,888

5,020

Accrued warranty

4,647

4,381

Contingent inventory reserves

3,700

3,806

Accrued royalty payments

2,583

2,195

Accrued TVN VDP, current(1)

^[1]

2,446

3,186

Accrued Avid litigation settlement, current

1,500

Others

15,707

13,703

Accrued Liabilities, Current

$ 51,221

$ 48,705

[1]	See Note 8, “Restructuring and related charges-TVN VDP,” for additional information on the Company’s TVN VDP liabilities.

Goodwill and Intangible Assets - Narratives (Details)		6 Months Ended
Goodwill and Intangible Assets - Narratives (Details)	Oct. 31, 2017 USD ($)	Jun. 29, 2018 ReportingUnit
Goodwill [Line Items]
Number of Reporting Units \| ReportingUnit		2
Goodwill, Impairment Loss \| $	$ 0

Goodwill and Identified Intangible Assets - Changes in Carrying Amount of Goodwill (Detail) $ in Thousands	6 Months Ended
	Jun. 29, 2018 USD ($)
Goodwill [Line Items]
Balance at beginning of period	$ 242,827
Foreign currency translation adjustment	(1,651)
Balance at end of period	241,176
Video [Member]
Goodwill [Line Items]
Balance at beginning of period	182,012
Foreign currency translation adjustment	(1,633)
Balance at end of period	180,379
Cable Access [Member]
Goodwill [Line Items]
Balance at beginning of period	60,815
Foreign currency translation adjustment	(18)
Balance at end of period	$ 60,797

Goodwill and Identified Intangible Assets - Summary of Goodwill and Identified Intangible Assets (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 29, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 85,655	$ 85,857
Accumulated Amortization	(68,645)	(64,578)
Total future amortization expense	$ 17,010	21,279
Developed Core Technology
Finite-Lived Intangible Assets [Line Items]
Useful Life	1 year 8 months 12 days
Gross Carrying Amount	$ 31,707	31,707
Accumulated Amortization	(22,985)	(20,396)
Total future amortization expense	$ 8,722	11,311
Customer relationships/contracts
Finite-Lived Intangible Assets [Line Items]
Useful Life	2 years 8 months 12 days
Gross Carrying Amount	$ 44,690	44,819
Accumulated Amortization	(36,664)	(35,205)
Total future amortization expense	$ 8,026	9,614
Trademarks and Trade Names
Finite-Lived Intangible Assets [Line Items]
Useful Life	1 year 8 months 12 days
Gross Carrying Amount	$ 630	654
Accumulated Amortization	(368)	(300)
Total future amortization expense	262	354
Maintenance Agreements and Related Relationships
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	5,500	5,500
Accumulated Amortization	(5,500)	(5,500)
Total future amortization expense	0	0
Order Backlog
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	3,128	3,177
Accumulated Amortization	(3,128)	(3,177)
Total future amortization expense	$ 0	$ 0

Goodwill and Identified Intangible Assets - Amortization Expense for Identifiable Purchased Intangible Assets (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 29, 2018	Jun. 30, 2017	Jun. 29, 2018	Jun. 30, 2017
Acquired Finite-Lived Intangible Assets [Line Items]
Included in cost of revenue	$ 1,295	$ 1,295	$ 2,590	$ 2,590
Included in operating expenses	800	780	1,604	1,554
Total amortization expense	$ 2,095	$ 2,075	$ 4,194	$ 4,144

Goodwill and Identified Intangible Assets - Estimated Future Amortization Expense of Purchased Intangible Assets (Detail) - USD ($) $ in Thousands	Jun. 29, 2018	Dec. 31, 2017
Acquired Finite-Lived Intangible Assets [Line Items]
2018 (remaining six months)	$ 4,174
2019	8,347
2020	3,987
2021	502
Total future amortization expense	17,010	$ 21,279
Cost of Sales [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
2018 (remaining six months)	2,590
2019	5,180
2020	951
2021	0
Total future amortization expense	8,721
Operating Expense [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
2018 (remaining six months)	1,584
2019	3,167
2020	3,036
2021	502
Total future amortization expense	$ 8,289

Restructuring and Related Charges Restructuring and Related Charges, COS & OPEX (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 29, 2018	Jun. 30, 2017	Jun. 29, 2018	Jun. 30, 2017
Restructuring and Related Activities [Abstract]
Production Related Impairments or Charges	$ 115	$ 278	$ 877	$ 786
Restructuring and related charges	631	777	1,717	2,056
Restructuring Charges	$ 746	$ 1,055	$ 2,594	$ 2,842

Restructuring and Related Charges - Additional Information (Detail)
$ in Thousands

1 Months Ended

3 Months Ended

6 Months Ended

12 Months Ended

Jan. 31, 2016

USD ($)

Jun. 29, 2018

USD ($)

Jun. 30, 2017

USD ($)

Jun. 29, 2018

USD ($)

Employees

Jun. 30, 2017

USD ($)

Dec. 31, 2017

USD ($)

Dec. 31, 2016

USD ($)

Employees

Jan. 04, 2016

USD ($)

$ 6,100

$ 8,000

3,500

4,400

2,600

3,600

Harmonic 2017 Restructuring Plan [Member]

631

$ 777

1,717

$ 2,056

Harmonic 2016 Restructuring Plan [Member]

2,500

5,835

7,554

^[1]

3,346

^[1]

2,489

$ 20,000

2,155

Facility Closing [Member] | Harmonic 2017 Restructuring Plan [Member]

543

200

Facility Closing [Member] | Harmonic 2016 Restructuring Plan [Member]

400

1,990

2,426

^[1]

900

^[1]

1,090

2,200

502

Employee Severance And Benefit Arrangements [Member] | Harmonic 2016 Restructuring Plan [Member]

Number of positions eliminated | Employees

$ 17,800

118

Employee Severance [Member] | Harmonic 2018 Restructuring Plan [Member]

100

Number of positions eliminated | Employees

$ 1,800

Employee Severance [Member] | Harmonic 2017 Restructuring Plan [Member]

$ 1,700

TVN Voluntary Departure Plan [Member] | Harmonic 2016 Restructuring Plan [Member]

2,100

3,845

5,128

^[1]

2,446

^[1]

1,399

1,653

477

TVN [Member]

Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Curtailment

$ 2,000

Postemployment Benefits Liability

3,400

5,100

TVN [Member] | Employee Severance And Benefit Arrangements [Member] | Harmonic 2016 Restructuring Plan [Member]

Number of positions eliminated | Employees

TVN [Member] | TVN Voluntary Departure Plan [Member]

Postemployment Benefits Liability

Restructuring charges

500

$ 1,800

$ 3,800

San Jose CA Excess Facility [Member] | Facility Closing [Member] | Harmonic 2016 Restructuring Plan [Member]

Fair Value of Excess Facility Restructuring

Restructuring charges

$ 1,400

$ 2,500

Deferred Rent Credit

$ 1,100

$ 1,200

[1]	The current portion and long-term portion of the restructuring liability are reported as components of “Accrued and other current liabilities” and “Other non-current liabilities”, respectively, on the Company’s Condensed Consolidated Balance Sheets.

Restructuring and Related Charges - 2016 Activities in Restructuring Accrual (Detail) - USD ($)
$ in Thousands

3 Months Ended

6 Months Ended

Jun. 29, 2018

Jun. 30, 2017

Jun. 29, 2018

Jun. 30, 2017

Dec. 31, 2017

$ 115

$ 278

$ 877

$ 786

8,000

631

$ 777

1,717

$ 2,056

6,100

8,000

$ 8,000

(3,500)

(4,400)

Harmonic 2016 Restructuring Plan [Member]

2,600

3,600

7,554

Foreign exchange gain (loss)

543

Cash payments

(2,155)

(107)

5,835

7,554

^[1]

(3,346)

Harmonic 2016 Restructuring Plan [Member] | Facility Closing [Member]

^[1]

2,489

2,426

Cash payments

(502)

1,990

2,426

^[1]

(900)

Harmonic 2016 Restructuring Plan [Member] | TVN Voluntary Departure Plan [Member]

^[1]

1,090

5,128

Foreign exchange gain (loss)

477

Cash payments

(1,653)

(107)

3,845

$ 5,128

^[1]

(2,446)

^[1]

$ 1,399

[1]	The current portion and long-term portion of the restructuring liability are reported as components of “Accrued and other current liabilities” and “Other non-current liabilities”, respectively, on the Company’s Condensed Consolidated Balance Sheets.

Convertible Notes, Other Debts And Capital Leases - Additional Information (Detail)
$ / shares in Units, shares in Millions

3 Months Ended

6 Months Ended

12 Months Ended

Dec. 14, 2015

Jun. 29, 2018

USD ($)

$ / shares

Jun. 29, 2018

USD ($)

$ / shares

Dec. 31, 2015

USD ($)

day

$ / shares

Dec. 31, 2017

USD ($)

Jun. 30, 2017

$ / shares

Debt Instrument, Interest Rate, Stated Percentage

4.00%

Debt Instrument, Face Amount

$ 128,250,000

Debt Instrument, Convertible, Conversion Ratio

173.9978

Debt Conversion, Converted Instrument, Amount

$ 1,000

Debt Instrument, Convertible, Conversion Price | $ / shares

$ 5.75

Debt Issuance Cost, Gross, Noncurrent

$ 4,100,000

Percentage Of Principal Amount Of Convertible Notes Is Equal To Repurchase Price

100.00%

Term loans

$ 1,081,000

1,282,000

Financing from French government agencies related to various government incentive programs (1)

^[1]

14,401,000

20,565,000

Carrying amount of equity component

26,062,000

Stock price greater or equal 130 percent of Note Conversion Price [Member]

Debt Instrument, Convertible, Threshold Trading Days | day

Debt Instrument, Convertible, Threshold Consecutive Trading Days | day

Debt Instrument, Convertible, Threshold Percentage of Stock Price Trigger

130.00%

Note price less than 98 percent of stock price times conversion rate [Member]

Debt Instrument, Convertible, Threshold Trading Days | day

Debt Instrument, Convertible, Threshold Consecutive Trading Days | day

Debt Instrument, Convertible, Threshold Percentage of Stock Price Trigger

98.00%

Privately Negotiated Transactions [Member]

Proceeds from Convertible Debt

$ 49,900,000

Stock Repurchased and Retired During Period, Shares | shares

11.1

TVN [Member]

Proceeds from Convertible Debt

$ 74,200,000

Income Taxes Receivable

$ 24,000,000

Loans Backed By French Research And Development Tax Credit Receivables [Member] | TVN [Member]

Debt Instrument, Interest Rate, Stated Percentage

0.60%

Adjusted EURIBOR Rate, Term

1 month

Debt Instrument, Basis Spread on Variable Rate

1.30%

Financing from French government agencies related to various government incentive programs (1)

^[1]

$ 12,000,000

$ 17,700,000

Loans From French Government For R&D Innovation Projects [Member]

Financing from French government agencies related to various government incentive programs (1)

^[1]

2,400,000

Revolving Credit Facility [Member] | Silicon Valley Bank [Member]

Line of Credit Facility, Current Borrowing Capacity

15,000,000

Minimum Net Worth Required for Compliance

20,000,000

Line of Credit Facility, Fair Value of Amount Outstanding

$ 0

Outstanding Borrowing Limit Based on Eligible Receivables, Percentage

85.00%

Covenant Ratio of Short Term Asset to Short Term Liabilities

110.00%

Minimum Liquidity Amount

$ 10,000,000

Letters of Credit Outstanding, Amount

$ 2,400,000

London Interbank Offered Rate (LIBOR) [Member] | Revolving Credit Facility [Member] | Silicon Valley Bank [Member]

Debt Instrument, Basis Spread on Variable Rate

2.25%

Not Comply with Liquidity Requirement [Member] | Prime Rate [Member] | Revolving Credit Facility [Member] | Silicon Valley Bank [Member]

Debt Instrument, Basis Spread on Variable Rate

0.25%

[1]

As of June 29, 2018 and December 31, 2017, loans backed by French R&D tax credit receivables were $12.0 million and $17.7 million, respectively. As of June 29, 2018, the TVN French Subsidiary had an aggregate of $24.0 million of R&D tax credit receivables from the French government from 2018 through 2022. See Note 6, “Balance Sheet Components” for additional information. These tax loans have a fixed rate of 0.6%, plus EURIBOR 1 month + 1.3% and mature between 2018 through 2020. The remaining loans of $2.4 million at June 29, 2018, primarily relate to financial support from French government agencies for R&D innovation projects at minimal interest rates, and these loans mature between 2018 through 2025.

Convertible Notes, Other Debts And Capital Leases - Convertible Note Roll Forward (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 29, 2018	Dec. 31, 2017	Dec. 31, 2015
Debt Instrument [Line Items]
Principal amount	$ 128,250	$ 128,250	$ 128,250
Less: Debt discount, net of amortization	(14,767)	(17,404)
Less: Debt issuance costs, net of amortization	(1,781)	(2,098)
Carrying amount	$ 111,702	$ 108,748
Remaining amortization period (years)	2 years 4 months 24 days	2 years 10 months 28 days
Effective interest rate on liability component	9.94%	9.94%
Carrying amount of equity component	$ 26,062	$ 26,062

Convertible Notes, Other Debts And Capital Leases - Interest (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 29, 2018	Jun. 30, 2017	Jun. 29, 2018	Jun. 30, 2017
Debt Disclosure [Abstract]
Contractual interest expense	$ 1,282	$ 1,282	$ 2,565	$ 2,565
Amortization of debt discount	1,340	1,214	2,637	2,388
Amortization of debt issuance costs	161	146	317	288
Total interest expense recognized	$ 2,783	$ 2,642	$ 5,519	$ 5,241

Convertible Notes , Other Debts And Capital Leases - Other Debt and Capital Lease Obligations (Details) - USD ($)
$ in Thousands

Jun. 29, 2018

Dec. 31, 2017

Financing from French government agencies related to various government incentive programs (1)

^[1]

$ 14,401

$ 20,565

Term loans

1,081

1,282

Obligations under capital leases

559

1,099

Total debt obligations

16,041

22,946

Less: current portion

(1,723)

(7,610)

Long-term portion

$ 14,318

$ 15,336

[1]

Convertible Notes, Other Debts And Capital Leases - Debt Maturities (Details) $ in Thousands	Jun. 29, 2018 USD ($)
Debt Disclosure [Abstract]
Capital Leases, Future Minimum Payments, Remainder of Fiscal Year	$ 395
Long-term Debt, Maturities, Repayments of Principal, Remainder of Fiscal Year	864
Capital Leases, Future Minimum Payments Due in Two Years	92
Long-term Debt, Maturities, Repayments of Principal in Year Two	6,879
Capital Leases, Future Minimum Payments Due in Three Years	49
Long-term Debt, Maturities, Repayments of Principal in Year Three	6,687
Capital Leases, Future Minimum Payments Due in Four Years	23
Long-term Debt, Maturities, Repayments of Principal in Year Four	497
Capital Leases, Future Minimum Payments Due in Five Years	0
Long-term Debt, Maturities, Repayments of Principal in Year Five	457
Capital Leases, Future Minimum Payments Due Thereafter	0
Long-term Debt, Maturities, Repayments of Principal after Year Five	98
Capital Leases, Future Minimum Payments Due	559
Long-term Debt	$ 15,482

Employee Benefit Plans and Stock-based Compensation - Additional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 29, 2018	Jun. 30, 2017	Jun. 29, 2018	Jun. 30, 2017	Dec. 31, 2017	Jan. 01, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee Service Share-based Compensation, Tax Benefit from Exercise of Stock Options	$ 0	$ 0	$ 0	$ 0
Total stock-based compensation	3,012,000	$ 4,136,000	8,769,000	7,387,000
Defined Benefit Plan, Benefit Obligation	5,000,000		5,000,000		$ 5,000,000
Liability, Defined Benefit Pension Plan, Current	100,000		100,000
Liability, Defined Benefit Pension Plan, Noncurrent	4,900,000		$ 4,900,000
Discretionary contributions of plan			25.00%
Percent of employees' gross pay eligible for matching			4.00%
Maximum contribution amount per participant			$ 1,000
Contributions in period			214,000	$ 285,000
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized	$ 13,300,000		$ 13,300,000
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition			1 year 9 months 18 days
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common Stock, Capital Shares Reserved for Future Issuance	1,800,000		1,800,000
Expected term (years)		4 years 3 months 18 days		4 years 3 months 18 days
Volatility		43.00%		43.00%
Risk-free interest rate		1.70%		1.70%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate		0.00%		0.00%
Performance-based Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period			969,598
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period			869,598
Total stock-based compensation	$ 100,000		$ 3,400,000
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Stock Options	$ 300,000		$ 300,000
Market-based awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period	40,000				344,500
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period			0
Total stock-based compensation	$ 100,000		$ 200,000
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	18 months				3 years
Aggregate Grant Date Fair Value of Market-Based Restricted Stock Units	$ 1,300,000		1,300,000
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Share-based Awards Other than Options	$ 100,000		$ 100,000
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Additional Shares Authorized			1,300,000
Common Stock, Capital Shares Reserved for Future Issuance	5,300,000		5,300,000
Discount Percentage On Purchase Of Stock			15.00%
Percentage of fair market value of Common Stock to purchase shares			85.00%
Value Of Stock Purchase Right Percentage Of Put Option			15.00%
Equity Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants in Period, Number of Shares			0
TVN [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Payment for Pension and Other Postretirement Benefits			$ 0
Director Option Plans 2002 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Additional Shares Authorized			400,000
Accounting Standards Update 2016-09 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Modified Retrospective Cumulative Effect Adjustment to Retained Earnings						$ 69,000

Employee Benefit Plans and Stock-based Compensation - Summary of Stock Options Outstanding (Detail) - Stock Options Outstanding [Member] $ / shares in Units, shares in Thousands	6 Months Ended
	Jun. 29, 2018 USD ($) $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Beginning balance \| shares	3,880
Weighted Average Exercise Price, Beginning balance \| $ / shares	$ 6.04
Grants in Period, Number of Shares \| shares	0
Grants in Period, Weighted Average Exercise Price Per Share \| $ / shares	$ 0.00
Number of Shares, Options exercised \| shares	(87)
Weighted Average Exercise Price, Options exercised \| $ / shares	$ 2.94
Number of Shares, Forfeited or cancelled \| shares	(35)
Weighted Average Exercise Price, Forfeited or cancelled \| $ / shares	$ 4.76
Canceled or expired \| shares	(538)
Canceled or Expired, Weighted Average Exercise Price \| $ / shares	$ 8.75
Number of Shares, Ending balance \| shares	3,220
Weighted Average Exercise Price, Ending balance \| $ / shares	$ 5.69
Weighted Average Remaining Contractual Term	2 years 9 months 18 days
Aggregate Intrinsic Value \| $	$ 866,800
Number of Shares, Vested and expected to vest \| shares	3,208
Weighted Average Exercise Price, Vested and expected to vest \| $ / shares	$ 5.69
Weighted Average Remaining Contractual Term (Years), Vested and expected to vest	2 years 9 months 18 days
Aggregate Intrinsic Value, Vested and expected to vest \| $	$ 859,300
Number of Shares, Exercisable \| shares	2,958
Weighted Average Exercise Price, Exercisable \| $ / shares	$ 5.77
Weighted Average Remaining Contractual Term (Years), Exercisable	2 years 8 months 12 days
Aggregate Intrinsic Value, Exercisable \| $	$ 696,100

Employee Benefit Plans and Stock-based Compensation - Summary of Restricted Stock Units Outstanding (Detail) - Restricted Stock Units Outstanding [Member] shares in Thousands	6 Months Ended
	Jun. 29, 2018 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Units, Beginning balance \| shares	2,904
Weighted Average Grant Date Fair Value, Beginning balance \| $ / shares	$ 5.09
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period \| shares	3,293
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value \| $ / shares	$ 3.74
Number of Units, Shares released \| shares	(2,220)
Vested in Period, Weighted Average Grant Date Fair Value \| $ / shares	$ 4.75
Number of Units, Forfeited or cancelled \| shares	(183)
Weighted Average Grant Date Fair Value, Forfeited or cancelled \| $ / shares	$ 5.09
Number of Units, Ending balance \| shares	3,794
Weighted Average Grant Date Fair Value, Ending balance \| $ / shares	$ 4.12

Employee Benefit Plans and Stock-based Compensation - Summary of Projected Benefit Obligation (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 29, 2018	Jun. 30, 2017	Jun. 29, 2018	Jun. 30, 2017
Employee Benefits and Share-based Compensation, Noncash [Abstract]
Service cost	$ 63	$ 55	$ 126	$ 110
Interest cost	19	16	38	32
Recognized net actuarial loss	0	2	0	3
Net periodic benefit cost included in operating loss	$ 82	$ 73	$ 164	$ 145

Employee Benefit Plans and Stock-based compensation - Stock-based Compensation in Opex (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 29, 2018	Jun. 30, 2017	Jun. 29, 2018	Jun. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation	$ 3,012	$ 4,136	$ 8,769	$ 7,387
Cost of Sales [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation	448	700	963	1,145
Research and Development Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation	818	1,337	2,622	2,314
Selling, General and Administrative Expenses [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation	1,746	2,099	5,184	3,928
Operating Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation	$ 2,564	$ 3,436	$ 7,806	$ 6,242

Employee Benefit Plans and Stock-based Compensation - Valuation Assumptions for Stock Options (Details) - Stock Options [Member]	3 Months Ended	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (years)	4 years 3 months 18 days	4 years 3 months 18 days
Volatility	43.00%	43.00%
Risk-free interest rate	1.70%	1.70%
Expected dividends	0.00%	0.00%

Employee Benefit Plans and Stock-based Compensation - Summary of Stock Awards Valuation Assumptions (Details) - Employee Stock Purchase Plan - $ / shares	6 Months Ended
	Jul. 02, 2018	Jul. 03, 2017
Purchase Period July 3, 2017 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (years)		6 months 1 day
Volatility		41.00%
Risk-free interest rate		1.00%
Expected dividends		0.00%
Estimated weighted average fair value per share at purchase date		$ 1.40
Scenario, Forecast [Member] \| Purchase Period July 2, 2018 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (years)	6 months 1 day
Volatility	60.00%
Risk-free interest rate	1.70%
Expected dividends	0.00%
Estimated weighted average fair value per share at purchase date	$ 1.34

Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
Income Taxes (Details) - USD ($) $ in Thousands	Jun. 29, 2018	Jun. 30, 2017	Jun. 29, 2018	Jun. 30, 2017
Income Tax Disclosure [Abstract]
Loss before income taxes	$ (2,022)	$ (30,921)	$ (14,638)	$ (55,180)
Provision for income taxes	$ 891	$ 579	$ 1,969	$ 347
Effective income tax rate	(44.10%)	(1.90%)	(13.50%)	(0.60%)

Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
	Jan. 01, 2017	Jun. 29, 2018	Jun. 30, 2017	Jun. 29, 2018	Jun. 30, 2017	Dec. 31, 2017	Mar. 31, 2017
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits		$ 17,900		$ 17,900
Effective income tax rate		(44.10%)	(1.90%)	(13.50%)	(0.60%)
Federal statutory income tax rate				21.00%
Unrecognized tax benefits that would impact the provision for income taxes		$ 1,100		$ 1,100
Interest and possible penalties related to uncertain tax positions		500		500
Decrease in Unrecognized Tax Benefits is Reasonably Possible		1,500		1,500
Accumulated deficit		$ (2,062,988)		$ (2,062,988)		$ (2,057,812)
Accounting Standards Update 2016-09 [Member]
Income Tax Contingency [Line Items]
Accumulated deficit	$ 0
Accounting Standards Update 2016-09 [Member] \| Deferred Tax Assets Gross
Income Tax Contingency [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	4,600
Accounting Standards Update 2016-09 [Member] \| Valuation Allowance of Deferred Tax Assets
Income Tax Contingency [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	4,600
Accounting Standards Update 2016-16 [Member]
Income Tax Contingency [Line Items]
Cumulative Effect on Retained Earnings, Net of Tax	$ 1,400
Deferred Tax Assets, Net							$ 1,100
Deferred Tax Assets, Valuation Allowance							2,100
Deferred Tax Assets, Tax Deferred Expense							$ 300

Net Loss Per Share - Numerators and Denominators of Basic and Diluted Net Income (Loss) Per Share Computations (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 29, 2018	Jun. 30, 2017	Jun. 29, 2018	Jun. 30, 2017
Numerator:
Net loss	$ (2,913)	$ (31,500)	$ (16,607)	$ (55,527)
Denominator:
Basic and diluted	85,304	80,590	84,616	80,203
Net loss per share:
Basic and diluted	$ (0.03)	$ (0.39)	$ (0.20)	$ (0.69)

Net Loss Per Share - Anti-dilutive Securities (Detail) - $ / shares

3 Months Ended

6 Months Ended

Jun. 29, 2018

Jun. 30, 2017

Jun. 29, 2018

Jun. 30, 2017

Dec. 31, 2015

Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]

Potential Common Shares Upon Notes Conversion If Only Settled In Shares

^[1]

7,883,000

9,374,000

7,706,000

8,974,000

22,304,348

Debt Instrument, Convertible, Conversion Price

$ 5.75

Stock Options [Member]

Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]

Restricted Stock Units (RSUs)

3,234,000

4,614,000

3,469,000

4,753,000

Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]

Employee Stock Purchase Plan

3,326,000

3,400,000

2,766,000

3,054,000

Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]

Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]

541,000

578,000

689,000

385,000

Warrant [Member]

^[2]

782,000

[1]

Excluded from the table above are the Notes, which are convertible under certain conditions into an aggregate of 22,304,348 shares of common stock. (See Note 9, “Convertible Notes, Other Debts and Capital Leases” for additional information on the Notes). Since the Company’s intent is to settle the principal amount of the Notes in cash, the treasury stock method is being used to calculate any potential dilutive effect of the conversion spread on diluted net income per share, if applicable. The conversion spread will have a dilutive impact on diluted net income per share when the Company’s average market price of its common stock for a given period exceeds the conversion price of $5.75 per share.

[2]

On September 26, 2016, in connection with the execution of a product supply agreement pursuant to which an affiliate of Comcast Corporation (together with Comcast Corporation, “Comcast”) may, in its sole discretion, purchase from the Company licenses to certain of the Company’s software products, the Company granted Comcast a warrant to purchase shares of its common stock. (See Note 13, “Warrants” for additional information).

Warrants (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 29, 2018	Jun. 30, 2017	Jun. 29, 2018	Jun. 30, 2017	Dec. 31, 2018	Sep. 26, 2016
Class of Warrant or Right [Line Items]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights						7,816,162
Class of Warrant or Right, Exercise Price of Warrants or Rights						$ 4.76
Fair Value Adjustment of Warrants	$ 284		$ 395
Comcast Product Supply Agreement [Member]
Class of Warrant or Right [Line Items]
Class of Warrant or Right, Outstanding						781,617
Fair Value Assumptions, Expected Dividend Rate			0.00%
Comcast Milestones Achievement [Member]
Class of Warrant or Right [Line Items]
Class of Warrant or Right, Unissued						1,954,042
Comcast Exceeding Specified Cumulative Purchase Volume [Member]
Class of Warrant or Right [Line Items]
Class of Warrant or Right, Unissued						1,172,425
Sales Revenue, Goods, Net [Member] \| Comcast Product Supply Agreement [Member]
Class of Warrant or Right [Line Items]
Fair Value Adjustment of Warrants	300	$ 0	$ 400	$ 400
Prepaid Expenses and Other Current Assets [Member]
Class of Warrant or Right [Line Items]
Prepaid Warrants Incentive	$ 600		$ 600
Scenario, Forecast [Member] \| Prepaid Expenses and Other Current Assets [Member]
Class of Warrant or Right [Line Items]
Prepaid Warrants Incentive					$ 1,000

Segment Information - Summary Financial Infomation by reportable segments (Details)
$ in Thousands

3 Months Ended

6 Months Ended

Jun. 29, 2018

USD ($)

Jun. 30, 2017

USD ($)

Jun. 29, 2018

USD ($)

segment

Jun. 30, 2017

USD ($)

$ 99,160

$ 82,315

$ 189,287

$ 165,258

51,603

33,815

98,786

74,223

Number of Reportable Segments | segment

642

(27,422)

$ (8,685)

(48,580)

Video [Member]

79,208

^[1]

73,379

$ 150,956

147,721

43,558

^[1]

37,720

84,784

78,493

6,239

^[1]

(8,947)

8,234

(14,783)

Cable Access [Member]

20,236

^[1]

8,936

38,726

17,537

10,187

^[1]

1,699

18,827

3,909

Operating Segments [Member]

540

^[1]

(7,411)

(973)

(13,491)

99,444

^[1]

82,315

189,682

165,258

53,745

^[1]

39,419

103,611

82,402

Operating Income (Loss) [Member]

$ 6,779

^[1]

(16,358)

$ 7,261

(28,274)

Prior period reclassification adjustment

$ 2,100

$ 3,200

[1]

The Company has historically employed an aggregate allocation methodology based on total revenues to attribute professional services revenue and sales expenses between its Video and Cable Access segments. Beginning in the fourth quarter of 2017, the Company has prospectively changed to a more precise attribution methodology as the activities of selling and supporting the CableOS solution have become increasingly distinct from those of Video solutions. The impact of making this change in the three and six months ended June 30, 2017 compared to the Company’s historical approach was an increase in operating loss of $2.1 million and $3.2 million, respectively, from the Video segment and a corresponding decrease in operating loss of the Cable Access segment. The Company believes that the updated allocation methodology will provide greater clarity regarding the operating metrics of the Video and Cable Access business segments.

Segment Information Segment Income or Loss Reconciliation (Details) - USD ($)
$ in Thousands

3 Months Ended

6 Months Ended

Jun. 29, 2018

Jun. 30, 2017

Jun. 29, 2018

Jun. 30, 2017

Unallocated Corporate Expenses

$ 642

$ (27,422)

$ (8,685)

$ (48,580)

Amortization of warrants

(284)

(395)

(50,961)

(61,237)

(107,471)

(122,803)

Stock-based compensation

(3,012)

(4,136)

(8,769)

(7,387)

Amortization of intangibles

(2,095)

(2,075)

(4,194)

(4,144)

Nonoperating Income (Expense)

(2,664)

(3,499)

(5,953)

(6,600)

Loss before income taxes

(2,022)

(30,921)

(14,638)

(55,180)

Operating Segments [Member]

Corporate, Non-Segment [Member]

6,779

^[1]

(16,358)

7,261

(28,274)