Fair Value Measurements - Financial Assets and Liabilities Measured at Fair Value Based on Three-Tier Fair Value Hierarchy (Detail) - USD ($)	Dec. 31, 2015		Dec. 31, 2014	Dec. 31, 2013
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total assets measured and recorded at fair value	$ 107,569,000		$ 57,915,000
Restricted cash (3)	1,093,000	[1]	0
Total liabilities measured and recorded at fair value	371,000		7,000
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	53,434,000		23,121,000
Cash equivalents [Member] | US Treasury Bill 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] | State, municipal and local government agencies bonds [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total assets measured and recorded at fair value			13,961,000
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	25,505,000		17,886,000
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	113,000		341,000
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	371,000		7,000
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	1,840,000		2,606,000
Level 1 [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total assets measured and recorded at fair value	80,272,000		25,727,000
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	53,434,000		23,121,000
Level 1 [Member] | Cash equivalents [Member] | US Treasury Bill 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] | State, municipal and local government agencies bonds [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] | 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	1,840,000		2,606,000
Level 2 [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total assets measured and recorded at fair value	27,297,000		32,188,000
Total liabilities measured and recorded at fair value	371,000		7,000
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 Bill 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] | State, municipal and local government agencies bonds [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Total assets measured and recorded at fair value			13,961,000
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	25,505,000		17,886,000
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	113,000		341,000
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	371,000		7,000
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	0		0
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 Bill 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] | State, municipal and local government agencies bonds [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] (3) 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.