Earnings Per Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Net Income	$ 27,761	$ 320,886	$ 50,439	$ 334,177
Weighted average shares outstanding - basic	62,289,437	62,112,936	62,265,941	62,095,670
Dilutive securities outstanding (in shares)	818,476	497,118	810,540	552,482
Weighted average shares outstanding - diluted (in shares)	63,107,913	62,610,054	63,076,481	62,648,152
Earnings per share - basic	$ 0.45	$ 5.17	$ 0.81	$ 5.38
Earnings per share - diluted	$ 0.44	$ 5.13	$ 0.80	$ 5.33
Weighted Average antidilutive securities outstanding (in shares)	26,668	10,359	24,208	14,369
Class of Warrant or Right, Number of Securities Called by Warrants or Rights	2,847,154		2,847,154		2,749,044
Class of Warrant or Right, Exercise Price of Warrants or Rights	13.39		13.39		13.86
Stock options [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Weighted Average antidilutive securities outstanding (in shares)	26,496	9,875	22,844	12,533
Restricted shares [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Weighted Average antidilutive securities outstanding (in shares)	172	484	1,364	1,836