CONSOLIDATED STATEMENT OF STOCKHOLDERS' EQUITY (USD $) In Thousands	Total	Common Stock	Additional Paid-in Capital	Retained Earnings
Beginning Balance at Dec. 31, 2010	$ 1,470,871	$ 1,098	$ 1,354,691	$ 115,082
Beginning Balance (in shares) at Dec. 31, 2010		109,754
Net income	121,988			121,988
Issuance of common stock (in shares)		2
Issuance of common stock	38		38
Retirement of common stock (in shares)		(10,560)
Retirement of common stock	(237,456)	(106)	(237,350)
Restricted stock compensation, net of forfeitures (in shares)		(18)
Restricted stock compensation, net of forfeitures	4,559		4,559
Income tax benefit of equity compensation	1,771		1,771
Stock option compensation expense, net of forfeitures	3,191		3,191
Restricted stock grant (in shares)		185
Restricted stock grant		2	(2)
Stock options exercised (in shares)		245
Stock options exercised	1,911	2	1,909
Ending Balance at Sep. 30, 2011	1,366,873	996	1,128,807	237,070
Ending Balance (in shares) at Sep. 30, 2011		99,608
Beginning Balance at Dec. 31, 2011	1,408,022	995	1,129,435	277,592
Beginning Balance (in shares) at Dec. 31, 2011		99,528
Net income	111,353			111,353
Issuance of common stock	19		19
Retirement of common stock (in shares)		(100)
Retirement of common stock	(2,481)	(1)	(2,480)
Dividends declared on common stock ($0.40 per share)	(40,138)			(40,138)
Restricted stock compensation, net of forfeitures (in shares)		(13)
Restricted stock compensation, net of forfeitures	5,604		5,604
Income tax benefit of equity compensation	2,191		2,191
Stock option compensation expense, net of forfeitures	3,493		3,493
Restricted stock grant (in shares)		332
Restricted stock grant		3	(3)
Stock options exercised (in shares)		301
Stock options exercised	4,015	3	4,012
Ending Balance at Sep. 30, 2012	$ 1,492,078	$ 1,000	$ 1,142,271	$ 348,807
Ending Balance (in shares) at Sep. 30, 2012		100,048