Fair Value Measurements - Valuation of Company's Assets and Liabilities Measured at Fair Value (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Fair Value Inputs Assets Liabilities Quantitative Information [Line Items]
Money market funds	$ 89,819	$ 83,519
Securities available-for-sale	14,479	51,208
Foreign currency forward and option contracts	227	15
Assets Fair Value Total	104,525	134,742
Municipal securities [Member]
Fair Value Inputs Assets Liabilities Quantitative Information [Line Items]
Securities available-for-sale	12,353	17,947
Corporate bonds [Member]
Fair Value Inputs Assets Liabilities Quantitative Information [Line Items]
Securities available-for-sale	2,126	2,157
U.S. government obligations [Member]
Fair Value Inputs Assets Liabilities Quantitative Information [Line Items]
Securities available-for-sale		31,104
Level 1 [Member]
Fair Value Inputs Assets Liabilities Quantitative Information [Line Items]
Money market funds	89,819	83,519
Foreign currency forward and option contracts
Assets Fair Value Total	89,819	83,519
Level 1 [Member] | Municipal securities [Member]
Fair Value Inputs Assets Liabilities Quantitative Information [Line Items]
Securities available-for-sale
Level 1 [Member] | Corporate bonds [Member]
Fair Value Inputs Assets Liabilities Quantitative Information [Line Items]
Securities available-for-sale
Level 1 [Member] | U.S. government obligations [Member]
Fair Value Inputs Assets Liabilities Quantitative Information [Line Items]
Securities available-for-sale
Level 2 [Member]
Fair Value Inputs Assets Liabilities Quantitative Information [Line Items]
Money market funds
Foreign currency forward and option contracts	227	15
Assets Fair Value Total	14,706	51,223
Level 2 [Member] | Municipal securities [Member]
Fair Value Inputs Assets Liabilities Quantitative Information [Line Items]
Securities available-for-sale	12,353	17,947
Level 2 [Member] | Corporate bonds [Member]
Fair Value Inputs Assets Liabilities Quantitative Information [Line Items]
Securities available-for-sale	2,126	2,157
Level 2 [Member] | U.S. government obligations [Member]
Fair Value Inputs Assets Liabilities Quantitative Information [Line Items]
Securities available-for-sale		31,104
Level 3 [Member]
Fair Value Inputs Assets Liabilities Quantitative Information [Line Items]
Money market funds
Foreign currency forward and option contracts
Assets Fair Value Total
Level 3 [Member] | Municipal securities [Member]
Fair Value Inputs Assets Liabilities Quantitative Information [Line Items]
Securities available-for-sale
Level 3 [Member] | Corporate bonds [Member]
Fair Value Inputs Assets Liabilities Quantitative Information [Line Items]
Securities available-for-sale
Level 3 [Member] | U.S. government obligations [Member]
Fair Value Inputs Assets Liabilities Quantitative Information [Line Items]
Securities available-for-sale