Consolidated Statements Of Stockholders' Equity (USD $) In Thousands, unless otherwise specified	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings (Deficit) [Member]	Total
Balance as of at Dec. 31, 2008	$ 1,247	$ 1,576,177	$ (197,065)	$ 1,380,359
Balance as of (shares) at Dec. 31, 2008	124,673
Comprehensive income:
Net income			154,954	154,954
Total comprehensive income			154,954	154,954
Issuance of common stock		50		50
Issuance of common stock, shares	3
Retirement of common stock	(103)	(123,631)		(123,734)
Retirement of common stock, shares	(10,314)
Amortization of restricted stock compensation, net of forfeitures		5,719		5,719
Amortization of restricted stock compensation, net of forfeitures, shares	(30)
Stock option compensation expense, net of forfeitures		4,059		4,059
Income tax benefit of equity compensation		5,973		5,973
Restricted stock grant	1	(1)
Restricted stock grant, shares	135
Stock options exercised	15	15,151		15,166
Stock options exercised, shares	1,495
Balance as of at Dec. 31, 2009	1,160	1,483,497	(42,111)	1,442,546
Balance as of (shares) at Dec. 31, 2009	115,962
Comprehensive income:
Net income			157,193	157,193
Total comprehensive income			157,193	157,193
Issuance of common stock		47		47
Issuance of common stock, shares	2
Retirement of common stock	(73)	(148,879)		(148,952)
Retirement of common stock, shares	(7,288)
Amortization of restricted stock compensation, net of forfeitures		5,508		5,508
Amortization of restricted stock compensation, net of forfeitures, shares	(26)
Stock option compensation expense, net of forfeitures		4,091		4,091
Income tax benefit of equity compensation		3,837		3,837
Restricted stock grant	3	(3)
Restricted stock grant, shares	293
Stock options exercised	8	6,593		6,601
Stock options exercised, shares	811
Balance as of at Dec. 31, 2010	1,098	1,354,691	115,082	1,470,871
Balance as of (shares) at Dec. 31, 2010	109,754
Comprehensive income:
Net income			162,510	162,510
Total comprehensive income			162,510	162,510
Issuance of common stock		51		51
Issuance of common stock, shares	3
Retirement of common stock	(107)	(239,618)		(239,725)
Retirement of common stock, shares	(10,661)
Amortization of restricted stock compensation, net of forfeitures		6,123		6,123
Amortization of restricted stock compensation, net of forfeitures, shares	(22)
Stock option compensation expense, net of forfeitures		4,210		4,210
Income tax benefit of equity compensation		1,845		1,845
Restricted stock grant	2	(2)
Restricted stock grant, shares	186
Stock options exercised	2	2,135		2,137
Stock options exercised, shares	268			268
Balance as of at Dec. 31, 2011	$ 995	$ 1,129,435	$ 277,592	$ 1,408,022
Balance as of (shares) at Dec. 31, 2011	99,528