Earnings Per Common 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
Earnings Per Common Share
Net income	$ 15,665	$ 12,824	$ 29,517	$ 22,820
Preferred stock dividends	(2,827)		(2,827)
Net income available to common shareholders	12,838	12,824	26,690	22,820
Income allocated to participating securities	(154)	(187)	(314)	(102)
Net income allocated to common shareholders	$ 12,684	$ 12,637	$ 26,376	$ 22,718
Basic weighted average common shares outstanding	97,021,334	95,332,904	96,848,989	95,175,886
Diluted weighted average common shares outstanding	97,021,334	95,332,904	96,848,989	95,175,886
Basic EPS (in dollars per share)	$ 0.13	$ 0.13	$ 0.27	$ 0.24
Diluted EPS (in dollars per share)	$ 0.13	$ 0.13	$ 0.27	$ 0.24
Stock options excluded from computation of earnings per share (in shares)	1,949,670	5,750,485	2,387,763	5,786,354