Earnings Per Share (Details 1) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2012		Jun. 30, 2011		Jun. 30, 2012		Jun. 30, 2011
Earnings Per Share [Abstract]
Net Income (Loss) Available to Common Stockholders, Diluted	$ 16,191		$ 23,000		$ 48,514		$ 65,179
Earnings per common share - Basic:
Net Income	16,324		23,309		48,926		65,986
Less: Distributed and undistributed earnings allocated to restricted common shares	(133)	[1]	(309)	[1]	(412)	[1]	(807)	[1]
Earnings available to common shareholders - Basic	16,191		23,000		48,514		65,179
Weighted-average common shares outstanding - Basic	71,723,014		75,701,045		71,709,976		77,234,869
Earnings per common share - Basic	$ 0.23		$ 0.30		$ 0.68		$ 0.84
Earnings per common share - Diluted:
Net Income	16,324		23,309		48,926		65,986
Less: Distributed and undistributed earnings allocated to restricted common shares	(133)	[1]	(309)	[1]	(412)	[1]	(807)	[1]
Earnings available to common shareholders - Basic	$ 16,191		$ 23,000		$ 48,514		$ 65,179
Weighted-average common shares outstanding - Basic	71,723,014		75,701,045		71,709,976		77,234,869
Effect of diluted shares	0	[2]	0	[2]	0	[2]	0	[2]
Weighted-average common shares outstanding - Diluted	71,723,014		75,701,045		71,709,976		77,234,869
Earnings per common share - Diluted	$ 0.23		$ 0.30		$ 0.68		$ 0.84

[1] For the three months ended June 30, 2011 and 2012, distributed and undistributed earnings to restricted shares is 1.33% and 0.81%, respectively, of net income. For the six months ended June 30, 2011 and 2012, distributed and undistributed earnings to restricted share is 1.22% and 0.84%, respectively. The amount of restricted share forfeitures for all periods present is immaterial to the allocation of distributed and undistributed earnings.

[2] For the three and six months ended June 30, 2011 and 2012, we have no dilutive shares.