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			71,524	71,524
Total comprehensive income			71,524	71,524
Issuance of common stock		22		22
Issuance of common stock, shares	1
Retirement of common stock	(46)	(91,373)		(91,419)
Retirement of common stock, shares	(4,514)
Amortization of restricted stock compensation, net of forfeitures		2,835		2,835
Amortization of restricted stock compensation, net of forfeitures, shares	(14)
Income tax benefit of equity compensation		1,713		1,713
Stock option compensation expense, net of forfeitures		1,984		1,984
Restricted stock grant	2	(2)
Restricted stock grant, shares	179
Stock options exercised	5	4,725		4,730
Stock options exercised, shares	509
Balance as of at Jun. 30, 2010	1,121	1,403,401	29,413	1,433,935
Balance as of (shares) at Jun. 30, 2010	112,123
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			82,748	82,748
Total comprehensive income			82,748	82,748
Issuance of common stock	1	25		25
Retirement of common stock	(30)	(72,437)		(72,467)
Retirement of common stock, shares	(2,984)
Amortization of restricted stock compensation, net of forfeitures		2,997		2,997
Amortization of restricted stock compensation, net of forfeitures, shares	(11)
Income tax benefit of equity compensation		1,692		1,692
Stock option compensation expense, net of forfeitures		2,209		2,209
Restricted stock grant	2	(2)
Restricted stock grant, shares	185
Stock options exercised	2	1,742		1,744
Stock options exercised, shares	224
Balance as of at Jun. 30, 2011	$ 1,072	$ 1,290,917	$ 197,830	$ 1,489,819
Balance as of (shares) at Jun. 30, 2011	107,169