Summary of Significant Accounting Policies - Additional Information (Detail) $ in Thousands					3 Months Ended	12 Months Ended
		Jan. 01, 2019 USD ($)		Jan. 01, 2017 USD ($)	Mar. 29, 2019 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($) Customer ReportingUnit segment	Dec. 31, 2018 USD ($) Customer	Dec. 31, 2017 USD ($)	Sep. 27, 2019 USD ($)	Dec. 31, 2015 USD ($)
Cash and cash equivalents maximum maturity							3 months
Investments in Equity Securities							$ 3,593	$ 3,593
Cash and cash equivalents							93,058	65,989	$ 57,024
Accounts receivable, net							88,500	81,795
Debts with French government agencies & other							17,224	19,859
Capitalized Software Development Costs for Software Sold to Customers							1,100	900	1,100
Hosting Arrangement, Service Contract, Implementation Cost, Capitalized, before Accumulated Amortization							3,600
Goodwill							$ 239,780	240,618	242,827
Number of reporting units | ReportingUnit							2
Goodwill, Impairment Loss							$ 0	0	0
Impairment of Intangible Assets, Finite-lived							0	0	0
Foreign Currency Cash Flow Hedge Derivative at Fair Value, Net							0	0
Advertising expense							$ 700	$ 1,000	700
Net Accumulated Gain or Loss as a Percentage of Projected Plan Benefit Obligation							10.00%
More Likely Than Not Threshold Recognition of Uncertain Tax Position							50.00%
Number of reportable segments | segment							2
Operating lease right-of-use assets							$ 27,491
Operating Lease, Liability							35,214
Operating Lease, Payments							$ 9,702
Furniture and Fixtures [Member]
Property, plant and equipment estimated useful life							5 years
Internal Use Software [Member]
Property, plant and equipment estimated useful life							3 years
Machinery and Equipment [Member]
Property, plant and equipment estimated useful life							4 years
Leasehold Improvements [Member]
Property, plant and equipment leasehold improvements useful lives							shorter of the remaining useful lives of the assets or the lease term of the respective assets
Leaseholds and Leasehold Improvements [Member] | Minimum [Member]
Lessee, Operating Lease, Term of Contract							1 year
Leaseholds and Leasehold Improvements [Member] | Maximum [Member]
Lessee, Operating Lease, Term of Contract							11 years
Foreign Exchange Forward [Member] | Not Designated as Hedging Instrument, Trading [Member]
Foreign Currency Derivative Instruments Not Designated as Hedging Instruments at Fair Value, Net							$ 0
Forward Contracts [Member]
Derivative, Term of Contract							12 months
Software [Member]
Property, plant and equipment estimated useful life							3 years
Accounts Receivable [Member]
Entity-wide revenue, major customer, revenue or accounts receivable percentage							10.00%	10.00%
TVN [Member]
Research and Development Tax Credits Receivables from French Government							$ 4,700	$ 5,900	5,900
Other Expense [Member]
Remeasurement Losses, Reporting Currency Denominated, Value							1,500	$ 600	$ 2,200
Accounting Standards Update 2016-09 [Member]
Cumulative Effect on Retained Earnings, Net of Tax	[1]	$ 1,400
Accounting Standards Update 2016-02 [Member]
Operating lease right-of-use assets		23,300
Operating Lease, Liability		23,300
Operating Lease, Payments		0
Accounting Standards Update 2018-07 [Member]
Cumulative Effect on Retained Earnings, Net of Tax	[1]				$ 1,400
JPMORGAN CHASE BANK N.A. [Member] | Revolving Credit Facility [Member]
Line of Credit Facility, Current Borrowing Capacity							$ 0
Debt Instrument, Interest Rate, Stated Percentage							1.25%
JPMORGAN CHASE BANK N.A. [Member] | Revolving Credit Facility [Member] | Maximum [Member]
Line of Credit Facility, Current Borrowing Capacity							$ 25,000
Cash Flow Hedging [Member] | Forward Contracts [Member] | Designated as Hedging Instrument [Member]
Derivative, Term of Contract							12 months
Retained Earnings [Member] | Accounting Standards Update 2016-09 [Member]
Cumulative Effect on Retained Earnings, Net of Tax		1,400	[1]	$ (69)
Retained Earnings [Member] | Accounting Standards Update 2016-02 [Member]
Cumulative Effect on Retained Earnings, Net of Tax		$ 0
Additional Paid-in Capital [Member] | Accounting Standards Update 2016-09 [Member]
Cumulative Effect on Retained Earnings, Net of Tax				$ 69
Forecast [Member]
Defined Benefit Plan, Actuarial Gain (Loss), Immediate Recognition as Component in Net Periodic Benefit (Cost) Credit						$ 0
Credit Concentration Risk [Member] | Accounts Receivable [Member]
Number of significant customers for accounts receivable | Customer							1	2
Convertible Note due 2024 [Member]
Debt Instrument, Face Amount							$ 115,500			$ 115,500
Debt Instrument, Interest Rate, Stated Percentage							2.00%			2.00%
Convertible Note due 2020 [Member]
Debt Instrument, Face Amount							$ 45,785	$ 128,250			$ 128,250
Debt Instrument, Interest Rate, Stated Percentage							4.00%				4.00%
Comcast [Member] | Net Revenue [Member]
Entity-wide revenue, major customer, revenue or accounts receivable percentage							10.00%	10.00%
Comcast [Member] | Customer Concentration Risk [Member] | Net Revenue [Member]
Number Of Customers Accounting For More Than Ten Percent of Revenue | Customer							1	1
Entity-wide revenue, major customer, revenue or accounts receivable percentage							23.00%	15.00%

[1] See Note 2, “Summary of Significant Accounting Policies-Recently Adopted Accounting Pronouncements,” for more information on the adoption of ASC 718, Compensation-Stock Compensation (“Topic 718”) issued by the Financial Accounting Standards Board.