Fair Value Measurements - Schedule of Fair Value of Assets and Liabilities Measured on Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives - currency forward contracts	$ 1,240	$ 1,966
Derivatives - currency forward contracts	318
Cash and cash equivalents	95,212	167,517
Short-term investments	158,631us-gaap_ShortTermInvestments	129,594us-gaap_ShortTermInvestments
Other current assets	1,240	1,966
Long-term investments	237,313	157,201
Other current liabilities	318
Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives - currency forward contracts	1,240	2,110
Total assets	485,073	418,828
Derivatives - currency forward contracts	318
Cash and cash equivalents	87,889	129,923
Short-term investments	158,631	129,594
Other current assets	1,240	2,110
Total current assets	247,760	261,627
Long-term investments	237,313	157,201
Other current liabilities	318
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]
Total assets	87,790	129,092
Cash and cash equivalents	87,790	129,092
Total current assets	87,790	129,092
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]
Derivatives - currency forward contracts	1,240	2,110
Total assets	397,283	289,736
Derivatives - currency forward contracts	318
Cash and cash equivalents	99	831
Short-term investments	158,631	129,594
Other current assets	1,240	2,110
Total current assets	159,970	132,535
Long-term investments	237,313	157,201
Other current liabilities	318
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	87,790	129,092
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	87,790	129,092
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	99	131
Available-for-sale securities\investments	327	82
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	99	131
Available-for-sale securities\investments	327	82
Time Deposits And Certificates of Deposit [Member] \| Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities\investments	5,400	20,948
Time Deposits And Certificates of Deposit [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\investments	5,400	20,948
Commercial Paper [Member] \| Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities\investments	1,447
Commercial Paper [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\investments	1,447
Asset Backed Securities [Member] \| Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities\investments	129,242	75,674
Asset Backed Securities [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\investments	129,242	75,674
Corporate Obligations [Member] \| Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents		700
Available-for-sale securities\investments	148,445	88,689
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]
Cash and cash equivalents		700
Available-for-sale securities\investments	148,445	88,689
Municipal Bonds [Member] \| Fair Value Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities\investments	7,678	3,353
Municipal Bonds [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\investments	7,678	3,353
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\investments	103,405	98,049
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\investments	$ 103,405	$ 98,049

Current assets fair value disclosure.

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Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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Investments in debt and equity securities which are categorized neither as held-to-maturity nor trading and which are intended to be sold or mature more than one year from the balance sheet date or operating cycle, if longer. Such securities are reported at fair value; unrealized gains (losses) related to Available-for-sale Securities are excluded from earnings and reported in a separate component of shareholders' equity (other comprehensive income), unless the Available-for-sale security is designated as a hedge or is determined to have had an other than temporary decline in fair value below its amortized cost basis. All or a portion of the unrealized holding gain (loss) of an Available-for-sale security that is designated as being hedged in a fair value hedge is recognized in earnings during the period of the hedge, as are other than temporary declines in fair value below the cost basis for investments in equity securities and debt securities that an entity intends to sell or it is more likely than not that it will be required to sell before the recovery of its amortized cost basis. Other than temporary declines in fair value below the cost basis for debt securities categorized as Available-for-sale that an entity does not intend to sell and for which it is not more likely than not that the entity will be required to sell before the recovery of its amortized cost basis are bifurcated into credit losses and losses related to all other factors. Other than temporary declines in fair value below cost basis related to credit losses are recognized in earnings, and losses related to all other factors are recognized in other comprehensive income.

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Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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Fair value as of the balance sheet date of all foreign currency derivative assets designated as cash flow hedging instruments.

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Fair value as of the balance sheet date of all foreign currency derivative liabilities designated as cash flow hedging instruments.

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Investments which are intended to be sold in the short term (usually less than one year or the normal operating cycle, whichever is longer) including trading securities, available-for-sale securities, held-to-maturity securities, and other short-term investments not otherwise listed in the existing taxonomy.

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