Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Net income	$ 15,756	$ 13,301	$ 29,563
Other comprehensive income (loss), net of tax:
Auction-rate securities valuation reserve adjustment, net of $0 tax in 2012, 2011 and 2010	140	270	160
Unrealized gain (loss) on available-for-sale securities, net of $0 tax in 2012, 2011 and 2010	34	(37)	104
Foreign currency translation adjustments, net of $0 tax in 2012, 2011 and 2010	408	1,381	1,361
Comprehensive income	$ 16,338	$ 14,915	$ 31,188