Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Net income	$ 35,495us-gaap_NetIncomeLoss	$ 22,898us-gaap_NetIncomeLoss	$ 15,756us-gaap_NetIncomeLoss
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustments	(609)	1,988	408
Total other comprehensive income (loss), net of tax	(449)	2,085	582
Comprehensive income	35,046us-gaap_ComprehensiveIncomeNetOfTax	24,983us-gaap_ComprehensiveIncomeNetOfTax	16,338us-gaap_ComprehensiveIncomeNetOfTax
Auction Rate Securities [Member]
Other comprehensive income (loss), net of tax:
Change in unrealized losses on securities, net of tax	179	130	140
Available-for-sale Securities [Member]
Other comprehensive income (loss), net of tax:
Change in unrealized losses on securities, net of tax	$ (19)	$ (33)	$ 34

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