Condensed Consolidated Statements of Comprehensive Income (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Net income	$ 11,221	$ 7,410	$ 26,635	$ 15,399
Other comprehensive income (loss), net of tax:
Change in unrealized losses on securities, net of tax			(65)
Foreign currency translation adjustments	(98)	431	(518)	1,595
Total other comprehensive income (loss), net of tax	(179)	614	(599)	1,724
Comprehensive income	11,042	8,024	26,036	17,123
Auction Rate Securities [Member]
Other comprehensive income (loss), net of tax:
Change in unrealized losses on securities, net of tax	(53)	149	(65)	117
Available-for-sale Securities [Member]
Other comprehensive income (loss), net of tax:
Change in unrealized losses on securities, net of tax	$ (28)	$ 34	$ (16)	$ 12