Condensed Consolidated Statements of Shareholders Equity (USD $) In Thousands, except Share data, unless otherwise specified	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]
Balance at Dec. 31, 2012	$ 3,163,699	$ 1,856	$ 1,226,835	$ 1,935,008
Balance, shares at Dec. 31, 2012	185,604,681	185,604,681
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	631,395			631,395
Allocated Share-based Compensation Expense			29,460
Stock-based compensation (unaudited)	29,460
Restricted stock:
Issued (unaudited)	2	2	0	0
Issued (unaudited), shares		166,200
Repurchased and canceled (unaudited)	(3,942)		(3,942)
Repurchased and canceled (unaudited), shares		(46,222)
Forfeited (unaudited), shares		(59,124)
Forfeitures (unaudited), value	(1)	(1)
Balance at Sep. 30, 2013	$ 3,820,613	$ 1,857	$ 1,252,353	$ 2,566,403
Balance, shares at Sep. 30, 2013	185,665,535	185,665,535