Consolidated Statement Of Stockholders' Equity (USD $) In Thousands	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings (Deficit) [Member]	Total
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			113,488	113,488
Total comprehensive income			113,488	113,488
Issuance of common stock		35		35
Issuance of common stock, shares	2
Retirement of common stock	(67)	(131,342)		(131,409)
Retirement of common stock, shares	(6,576)
Amortization of restricted stock compensation, net of forfeitures		4,134		4,134
Amortization of restricted stock compensation, net of forfeitures, shares	(19)
Income tax benefit of equity compensation		2,079		2,079
Stock option compensation expense, net of forfeitures		3,157		3,157
Restricted stock grant	2	(2)
Restricted stock grant, shares	179
Stock options exercised	6	5,130		5,136
Stock options exercised, shares	573
Balance as of at Sep. 30, 2010	1,101	1,366,688	71,377	1,439,166
Balance as of (shares) at Sep. 30, 2010	110,121
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			121,988	121,988
Total comprehensive income			121,988	121,988
Issuance of common stock		38		38
Issuance of common stock, shares	2
Retirement of common stock	(106)	(237,350)		(237,456)
Retirement of common stock, shares	(10,560)
Amortization of restricted stock compensation, net of forfeitures		4,559		4,559
Amortization of restricted stock compensation, net of forfeitures, shares	(18)
Income tax benefit of equity compensation		1,771		1,771
Stock option compensation expense, net of forfeitures		3,191		3,191
Restricted stock grant	2	(2)
Restricted stock grant, shares	185
Stock options exercised	2	1,909		1,911
Stock options exercised, shares	245
Balance as of at Sep. 30, 2011	$ 996	$ 1,128,807	$ 237,070	$ 1,366,873
Balance as of (shares) at Sep. 30, 2011	99,608