Earnings Per Common Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Earnings Per Common Share
Net income	$ 16,924	$ 13,355	$ 46,441	$ 36,175
Preferred stock dividends	(2,194)		(5,021)
Net income available to common shareholders	14,730	13,355	41,420	36,175
Income allocated to participating securities	(195)	(206)	(508)	(250)
Net income allocated to common shareholders	$ 14,535	$ 13,149	$ 40,912	$ 35,925
Basic weighted average common shares outstanding	97,199,329	95,555,816	96,967,052	95,303,453
Diluted weighted average common shares outstanding	97,199,329	95,555,816	96,967,052	95,303,453
Basic EPS (in dollars per share)	$ 0.15	$ 0.14	$ 0.42	$ 0.38
Diluted EPS (in dollars per share)	$ 0.15	$ 0.14	$ 0.42	$ 0.38
Stock options excluded from computation of earnings per share (in shares)	1,871,935	5,452,028	2,215,820	5,674,912