Net Income Per Common Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended												12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Net Income													$ 74,042		$ 39,812		$ 29,472
Preferred Stock Dividends, Income Statement Impact													2,036		0		3,061
Net Income (Loss) Available to Common Stockholders, Basic	18,330	18,353	18,847	16,476	14,406	1,532	13,594	10,280	9,647	5,966	6,264	4,534	72,006		39,812		26,411
Dilutive Securities, Effect on Basic Earnings Per Share, Other													0		0		3,061
Diluted, Income													72,006		39,812		29,472
Weighted Average Common Shares													53,146,416		38,579,780		17,595,022
Weighted Average Number Diluted Shares Outstanding Adjustment													0		799		3,324,014
Diluted, Weighted Average Number Common Shares													53,146,416		38,580,579		20,919,036
Basic Net Income Per Common Share	$ 0.34	$ 0.34	$ 0.35	$ 0.33	$ 0.36	$ 0.04	$ 0.34	$ 0.31	$ 0.41	$ 0.35	$ 0.41	$ 0.32	$ 1.35		$ 1.03		$ 1.50
Diluted Net Income Per Common Share	$ 0.34	$ 0.34	$ 0.35	$ 0.33	$ 0.36	$ 0.04	$ 0.34	$ 0.31	$ 0.40	$ 0.33	$ 0.38	$ 0.30	$ 1.35	[1]	$ 1.03	[1]	$ 1.41
Incremental Common Shares Attributable to Conversion of Preferred Stock																	3,319,395
Effect of dilutive stock options on weighted average common shares															799		4,619
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount													15,000
Accumulated Distributions in Excess of Net Income [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Net Income															$ 39,812		$ 29,472

[1] For the years ended December 31, 2012, December 31, 2011 and December 31, 2010, the calculation of diluted net income per common share excludes the effect of 15,000 unexercised stock option awards because their inclusion would have been anti-dilutive.