Fair Value Measurements - Schedule of Fair Value of Assets and Liabilities Measured on Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Derivatives - currency forward contracts	$ 746	$ 961
Liabilities Derivatives - currency forward contracts	749	1,310
Long-term investments	5,183	12,158
Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	57,982	51,307
Assets Derivatives - currency forward contracts	746	961
Total assets	429,787	392,027
Liabilities Derivatives - currency forward contracts	749	1,310
Short-term investments	365,876	327,601
Total current assets	424,604	379,869
Long-term investments	5,183	12,158
Other current liabilities	749	1,310
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] \| Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	57,982	51,291
Assets Derivatives - currency forward contracts
Total assets	254,216	347,747
Liabilities Derivatives - currency forward contracts
Short-term investments	191,107	284,298
Total current assets	249,089	335,589
Long-term investments	5,127	12,158
Other current liabilities
Significant Other Observable Inputs (Level 2) [Member] \| Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents		16
Assets Derivatives - currency forward contracts	746	961
Total assets	175,571	44,280
Liabilities Derivatives - currency forward contracts	749	1,310
Short-term investments	174,769	43,303
Total current assets	175,515	44,280
Long-term investments	56
Other current liabilities	749	1,310
Significant Unobservable Inputs (Level 3) [Member] \| Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents
Assets Derivatives - currency forward contracts
Total assets
Liabilities Derivatives - currency forward contracts
Short-term investments
Total current assets
Long-term investments
Other current liabilities
Money Market Funds [Member] \| Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	57,982	51,291
Money Market Funds [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] \| Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	57,982	51,291
Money Market Funds [Member] \| Significant Other Observable Inputs (Level 2) [Member] \| Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents
Money Market Funds [Member] \| Significant Unobservable Inputs (Level 3) [Member] \| Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents
Bankers' Acceptance Drafts [Member] \| Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents		16
Available-for-sale securities	330	242
Bankers' Acceptance Drafts [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] \| Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents
Available-for-sale securities
Bankers' Acceptance Drafts [Member] \| Significant Other Observable Inputs (Level 2) [Member] \| Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents		16
Available-for-sale securities	330	242
Bankers' Acceptance Drafts [Member] \| Significant Unobservable Inputs (Level 3) [Member] \| Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents
Available-for-sale securities
Mutual Funds [Member] \| Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mutual funds	959	791
Mutual Funds [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] \| Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mutual funds	959	791
Mutual Funds [Member] \| Significant Other Observable Inputs (Level 2) [Member] \| Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mutual funds
Mutual Funds [Member] \| Significant Unobservable Inputs (Level 3) [Member] \| Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mutual funds
U.S. Treasury Obligations [Member] \| Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		13,054
U.S. Treasury Obligations [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] \| Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities
U.S. Treasury Obligations [Member] \| Significant Other Observable Inputs (Level 2) [Member] \| Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities		13,054
U.S. Treasury Obligations [Member] \| Significant Unobservable Inputs (Level 3) [Member] \| Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities
U.S. Agency Obligations [Member] \| Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	210,829	325,672
U.S. Agency Obligations [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] \| Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	195,275	295,665
U.S. Agency Obligations [Member] \| Significant Other Observable Inputs (Level 2) [Member] \| Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	15,554	30,007
U.S. Agency Obligations [Member] \| Significant Unobservable Inputs (Level 3) [Member] \| Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities
Other Current Assets [Member] \| Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Derivatives - currency forward contracts	746	961
Other Current Assets [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] \| Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Derivatives - currency forward contracts
Other Current Assets [Member] \| Significant Other Observable Inputs (Level 2) [Member] \| Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Derivatives - currency forward contracts	746	961
Other Current Assets [Member] \| Significant Unobservable Inputs (Level 3) [Member] \| Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets Derivatives - currency forward contracts
Time Deposits [Member] \| Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	77,633
Time Deposits [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] \| Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities
Time Deposits [Member] \| Significant Other Observable Inputs (Level 2) [Member] \| Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	77,633
Time Deposits [Member] \| Significant Unobservable Inputs (Level 3) [Member] \| Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities
Commercial Paper and Corporate Obligations [Member] \| Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	81,308
Commercial Paper and Corporate Obligations [Member] \| Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] \| Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities
Commercial Paper and Corporate Obligations [Member] \| Significant Other Observable Inputs (Level 2) [Member] \| Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	81,308
Commercial Paper and Corporate Obligations [Member] \| Significant Unobservable Inputs (Level 3) [Member] \| Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities