Summary of Significant Accounting Policies - Additional Information (Detail)		3 Months Ended	12 Months Ended
	Jan. 01, 2017 USD ($)	Dec. 31, 2014 segment	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($) Customer ReportingUnit segment	Dec. 31, 2017 USD ($) Customer	Dec. 31, 2016 USD ($)	Jan. 01, 2019 USD ($)	Jan. 01, 2018 USD ($)	Sep. 29, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2015 USD ($)
Cash and cash equivalents maximum maturity				3 months	3 months	3 months
Restricted Cash				$ 0	$ 1,700,000
Restricted cash included in prepaid expenses and other current assets				0	530,000	$ 732,000
Cost Method Investments				3,593,000	3,593,000
Cash and cash equivalents				65,989,000	57,024,000	55,635,000
Accounts receivable, net				81,795,000	69,844,000
Debt Instrument, Face Amount				$ 128,250,000	128,250,000						$ 128,250,000
Debt Instrument, Interest Rate, Stated Percentage				4.00%							4.00%
Debt and Capital Lease Obligations				$ 19,859,000	22,946,000
Capitalized Software Development Costs for Software Sold to Customers				900,000	1,100,000
Goodwill				$ 240,618,000	242,827,000	237,279,000
Number of reporting units | ReportingUnit				2
Goodwill, Impairment Loss				$ 0	0	0
Research and Development Expense				89,163,000	95,978,000	98,401,000
Advertising expense				$ 1,000,000	$ 700,000	1,400,000
Net Accumulated Gain or Loss as a Percentage of Projected Plan Benefit Obligation				10.00%	10.00%
More Likely Than Not Threshold Recognition of Uncertain Tax Position				50.00%
Number of reportable segments | segment		2		2
Retained Earnings (Accumulated Deficit)				$ (2,067,416,000)	$ (2,057,812,000)
Capitalized Contract Cost, Net				1,600,000
Capitalized Contract Cost, Amortization				1,300,000
Contract with Customer, Liability, Revenue Recognized				46,900,000
Short-term investments				0	0
Impairment of Intangible Assets, Finite-lived				0
Foreign Currency Cash Flow Hedge Derivative at Fair Value, Net				$ 0	$ 0	0
Revenue, Practical Expedient, Incremental Cost of Obtaining Contract [true false]				true
Revenue, Practical Expedient, Initial Application and Transition, Nondisclosure of Transaction Price Allocation to Remaining Performance Obligation [true false]				true
Revenue, Practical Expedient, Financing Component [true false]				true
Lease, Practical Expedients, Package [true false]				true
Discount rate				1.70%	1.50%
Defined Benefit Plan, Benefit Obligation				$ 4,881,000	$ 5,033,000	4,264,000
Deferred Tax Assets, Net				8,695,000	10,462,000
Deferred Tax Assets, Valuation Allowance				$ 77,144,000	$ 77,756,000	74,480,000					$ 64,545,000
Minimum [Member]
Capitalized Contract Cost, Amortization Period								1 year
Maximum [Member]
Revenue, Remaining Performance Obligation, Optional Exemption, Remaining Duration				1 year
Revenue, Financing Payment Term				1 year
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
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]
Number of significant customers for accounts receivable | Customer				2	0
Entity-wide revenue, major customer, revenue or accounts receivable percentage				10.00%	10.00%
Net Revenue [Member]
Entity-wide revenue, major customer, revenue or accounts receivable percentage				10.00%	10.00%
TVN [Member]
Goodwill						41,670,000
R&D Tax Credits				$ 5,900,000	$ 5,900,000	6,100,000
Other Expense [Member]
Remeasurement Losses, Reporting Currency Denominated, Value				600,000	2,200,000	200,000
Prepaid Expenses and Other Current Assets [Member]
Capitalized Contract Cost, Net				1,100,000
Other Assets [Member]
Restricted Cash and Investments, Noncurrent					1,200,000
Other long-term assets[Member]
Capitalized Contract Cost, Net				500,000
Accounting Standards Update 2016-18 [Member]
Restricted Cash				0	$ 1,700,000	$ 1,800,000
Accounting Standards Update 2016-09 [Member] | Retained Earnings [Member]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Net Income	$ 0
Accounting Standards Update 2016-09 [Member] | Deferred Tax Assets Gross [Member]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Net Income	4,600,000
Accounting Standards Update 2014-09 [Member]
Accounts receivable, net								$ 71,625,000
Accounting Standards Update 2016-16 [Member]
Cumulative Effect on Retained Earnings, Net of Tax	1,434,000
Deferred Tax Assets, Net										$ 1,100,000
Deferred Tax Assets, Valuation Allowance										2,100,000
Deferred Tax Assets, Tax Deferred Expense										$ 300,000
Accounting Standards Update 2017-01 [Member]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification				0
Silicon Valley Bank [Member] | Revolving Credit Facility [Member]
Line of Credit Facility, Current Borrowing Capacity				$ 15,000,000					$ 15,000,000
Cash Flow Hedging [Member] | Forward Contracts [Member] | Designated as Hedging Instrument [Member]
Derivative, Term of Contract				12 months
Sales Commission Contract Costs [Member] | Accounting Standards Update 2014-09 [Member]
Retained Earnings (Accumulated Deficit)								$ 1,400,000
Practical Expedient, Expense As Incurred [Member] | Maximum [Member]
Capitalized Contract Cost, Amortization Period				1 year
Additional Paid-in Capital [Member] | Accounting Standards Update 2016-09 [Member]
Cumulative Effect on Retained Earnings, Net of Tax	$ 69,000
Scenario, Forecast [Member]
Defined Benefit Plan, Actuarial Gain (Loss), Immediate Recognition as Component in Net Periodic Benefit (Cost) Credit			$ 0
Scenario, Forecast [Member] | Accounting Standards Update 2016-02 [Member]
Operating Lease, Right-of-Use Asset							$ 23,000,000
Operating Lease, Liability							$ 23,000,000
Customer Concentration Risk [Member] | Net Revenue [Member] | Comcast [Member]
Entity-wide revenue, major customer, revenue or accounts receivable percentage				15.00%
Number Of Customers Accounting For More Than Ten Percent of Revenue | Customer				1	0