Financial Assets Measured at Fair Value on Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets measured and recorded at fair value	$ 153,001	$ 97,925
Total liabilities measured and recorded at fair value	4,603	491
Commercial Paper
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents	59,980	14,605
Short-term investments Commercial paper	19,995
Money Market Fund Deposits
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents	73,026	83,320
Foreign Exchange Forward
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative financial instruments Foreign exchange forward contracts	4,603	491
Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets measured and recorded at fair value	73,026	83,320
Fair Value, Inputs, Level 1 | Money Market Fund Deposits
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents	73,026	83,320
Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets measured and recorded at fair value	79,995	14,605
Total liabilities measured and recorded at fair value	4,603	491
Fair Value, Inputs, Level 2 | Commercial Paper
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Cash equivalents	59,980	14,605
Short-term investments Commercial paper	19,995
Fair Value, Inputs, Level 2 | Foreign Exchange Forward
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative financial instruments Foreign exchange forward contracts	$ 4,603	$ 491