Consolidated Statement of Stockholders' Equity and Comprehensive Income (Unaudited) (USD $) In Thousands	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)
Beginning Balance at Dec. 31, 2010	$ 1,068,531	$ 23,853	$ 454,499	$ 557,849	$ 32,330
Beginning Balance, shares at Dec. 31, 2010		47,706
Stock-based compensation	7,012	(29)	7,041
Stock-based compensation, shares		(59)
Excess income taxes from stock-based compensation	(612)		(612)
Net income	6,353			6,353
Net change in unrealized gains and losses on marketable securities, net of income taxes	(3,999)				(3,999)
Total comprehensive income (loss)	2,354
Ending Balance at Jun. 30, 2011	$ 1,077,285	$ 23,824	$ 460,928	$ 564,202	$ 28,331
Ending Balance, shares at Jun. 30, 2011		47,647