Fair Value Measurements - Financial Assets and Liabilities Measured at Fair Value Based on Three-Tier Fair Value Hierarchy (Detail) - USD ($)		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total assets measured and recorded at fair value		$ 16,087,000	$ 107,569,000
Restricted cash (3)	[1]	731,000	1,093,000
Total liabilities measured and recorded at fair value		9,690,000	371,000
Accrued TVN VDP, current (1)	[2]	6,597,000
Accrued TVN VDP, long-term (1)	[2]	3,053,000
Assets, Fair Value Disclosure, Nonrecurring		0	0	$ 0
Liabilities, Fair Value Disclosure, Nonrecurring		0	0	$ 0
Cash equivalents [Member] | Money market funds [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total assets measured and recorded at fair value		8,301,000	53,434,000
Cash equivalents [Member] | US Treasury Bond Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total assets measured and recorded at fair value			24,998,000
Short-term investments [Member] | Corporate bonds [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total assets measured and recorded at fair value		6,923,000	25,505,000
Short-term investments [Member] | Commercial paper [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total assets measured and recorded at fair value			1,099,000
Prepaid Expenses and Other Current Assets [Member] | Bank Time Deposits [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Restricted cash (3)			580,000
Prepaid Expenses and Other Current Assets [Member] | Foreign exchange forward contracts [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total assets measured and recorded at fair value		54,000	113,000
Accrued Liabilities [Member] | Foreign exchange forward contracts [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total liabilities measured and recorded at fair value		40,000	371,000
Cost-method Investments [Member] | Equity Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total assets measured and recorded at fair value		809,000	1,840,000
Level 1 [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total assets measured and recorded at fair value		9,110,000	80,272,000
Total liabilities measured and recorded at fair value		0	0
Level 1 [Member] | Cash equivalents [Member] | Money market funds [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total assets measured and recorded at fair value		8,301,000	53,434,000
Level 1 [Member] | Cash equivalents [Member] | US Treasury Bond Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total assets measured and recorded at fair value			24,998,000
Level 1 [Member] | Short-term investments [Member] | Corporate bonds [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total assets measured and recorded at fair value		0	0
Level 1 [Member] | Short-term investments [Member] | Commercial paper [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total assets measured and recorded at fair value			0
Level 1 [Member] | Prepaid Expenses and Other Current Assets [Member] | Foreign exchange forward contracts [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total assets measured and recorded at fair value		0	0
Level 1 [Member] | Accrued Liabilities [Member] | Foreign exchange forward contracts [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total liabilities measured and recorded at fair value		0	0
Level 1 [Member] | Cost-method Investments [Member] | Equity Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total assets measured and recorded at fair value		809,000	1,840,000
Level 2 [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total assets measured and recorded at fair value		6,977,000	27,297,000
Total liabilities measured and recorded at fair value		40,000	371,000
Level 2 [Member] | Cash equivalents [Member] | Money market funds [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total assets measured and recorded at fair value		0	0
Level 2 [Member] | Cash equivalents [Member] | US Treasury Bond Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total assets measured and recorded at fair value			0
Level 2 [Member] | Short-term investments [Member] | Corporate bonds [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total assets measured and recorded at fair value		6,923,000	25,505,000
Level 2 [Member] | Short-term investments [Member] | Commercial paper [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total assets measured and recorded at fair value			1,099,000
Level 2 [Member] | Prepaid Expenses and Other Current Assets [Member] | Bank Time Deposits [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Restricted cash (3)			580,000
Level 2 [Member] | Prepaid Expenses and Other Current Assets [Member] | Foreign exchange forward contracts [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total assets measured and recorded at fair value		54,000	113,000
Level 2 [Member] | Accrued Liabilities [Member] | Foreign exchange forward contracts [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total liabilities measured and recorded at fair value		40,000	371,000
Level 2 [Member] | Cost-method Investments [Member] | Equity Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total assets measured and recorded at fair value		0	0
Level 3 [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total assets measured and recorded at fair value		0	0
Total liabilities measured and recorded at fair value		9,650,000	0
Accrued TVN VDP, current (1)		6,597,000
Accrued TVN VDP, long-term (1)		3,053,000
Level 3 [Member] | Cash equivalents [Member] | Money market funds [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total assets measured and recorded at fair value		0	0
Level 3 [Member] | Cash equivalents [Member] | US Treasury Bond Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total assets measured and recorded at fair value			0
Level 3 [Member] | Short-term investments [Member] | Corporate bonds [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total assets measured and recorded at fair value		0	0
Level 3 [Member] | Short-term investments [Member] | Commercial paper [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total assets measured and recorded at fair value			0
Level 3 [Member] | Prepaid Expenses and Other Current Assets [Member] | Foreign exchange forward contracts [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total assets measured and recorded at fair value		0	0
Level 3 [Member] | Accrued Liabilities [Member] | Foreign exchange forward contracts [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total liabilities measured and recorded at fair value		0	0
Level 3 [Member] | Cost-method Investments [Member] | Equity Securities [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total assets measured and recorded at fair value		$ 0	$ 0

[1] The restricted cash balances are held as 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. Additionally, as of December 31, 2016, the Company had approximately $1.1 million of restricted cash for the bank guarantee associated with the TVN French Subsidiary’s office building lease. This amount is reported under “Other Long-term Assets” on the Company’s Consolidated Balance Sheets.

[2] See Note 11, “Restructuring and related charges-TVN VDP,” for additional information on the Company’s TVN VDP liabilities.