CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (USD $) In Thousands, except Share data, unless otherwise specified	Common Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Retained Earnings (Accumulated Deficit) [Member]	Total
Balance at Dec. 31, 2008	$ 575	$ 547,389	$ (2,813)	$ (72,045)	$ 473,106
Balance (in shares) at Dec. 31, 2008	57,499,000
Increase (decrease) in stockholders' equity [Roll Forward]
Shares issued to employees, officers and directors	6	2,474			2,480
Shares issued to employees, officers and directors (in shares)	550,000
Repurchases of common stock	(12)	(16,669)			(16,681)
Repurchases of common stock (in shares)	(1,169,000)				(1,169,000)
Stock-based compensation, net		7,048			7,048
Tax effect of stock-based compensation, net		(1,007)			(1,007)
Comprehensive income (loss):
Net income				36,607	36,607
Unrealized loss on investments			(300)		(300)
Defined benefit plans, net of tax			1,207		1,207
Comprehensive income					37,514
Balance at Dec. 31, 2009	569	539,235	(1,906)	(35,438)	502,460
Balance (in shares) at Dec. 31, 2009	56,880,000
Increase (decrease) in stockholders' equity [Roll Forward]
Shares issued to employees, officers and directors	13	12,113			12,126
Shares issued to employees, officers and directors (in shares)	1,360,000
Stock-based compensation, net		5,589			5,589
Tax effect of stock-based compensation, net		1,078			1,078
Comprehensive income (loss):
Net income				47,469	47,469
Unrealized loss on investments			(250)		(250)
Defined benefit plans, net of tax			145		145
Comprehensive income					47,364
Balance at Dec. 31, 2010	582	558,015	(2,011)	12,031	568,617
Balance (in shares) at Dec. 31, 2010	58,240,000				58,239,875
Increase (decrease) in stockholders' equity [Roll Forward]
Shares issued to employees, officers and directors	7	2,884			2,891
Shares issued to employees, officers and directors (in shares)	675,000
Stock-based compensation, net		4,490			4,490
Tax effect of stock-based compensation, net		1,235			1,235
Comprehensive income (loss):
Net income				67,394	67,394
Unrealized loss on investments			(100)		(100)
Defined benefit plans, net of tax			(1,248)		(1,248)
Comprehensive income					66,046
Balance at Dec. 31, 2011	$ 589	$ 566,624	$ (3,359)	$ 79,425	$ 643,279
Balance (in shares) at Dec. 31, 2011	58,915,000				58,914,802