CONSOLIDATED STATEMENT OF COMPREHENSIVE INCOME (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Statement of Other Comprehensive Income [Abstract]
Net income	$ 58,691	$ 66,716	$ 74,253
Net change in cumulative translation adjustment	129	10	(19)
Change in unrealized gains (losses) on available-for sale securities, net of tax	28	(98)	(302)
Other comprehensive income (losses)	157	(88)	(321)
Comprehensive income (loss)	$ 58,848	$ 66,628	$ 73,932