Equity and Earnings Per Share Reconciliation (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	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, 2011	Dec. 31, 2010	Dec. 31, 2009
Earnings per common share
Net earnings	$ 21,712	$ 22,383	$ 21,038	$ 16,600	$ 9,874	$ 17,927	$ 19,015	$ 16,119	$ 81,733	$ 62,935	$ 65,419
Less: Dividends on preferred stock and discount amortization											12,763
Net earnings available to common shareholders									81,733	62,935	52,656
Less: Net earnings allocated to restricted stock									292	217	179
Net earnings allocated to common shareholders (numerator)									81,733	62,935	52,656
Weighted Average Shares Outstanding (denominator)									105,143	105,880	92,955
Earnings per common share	$ 0.21	$ 0.21	$ 0.20	$ 0.16	$ 0.09	$ 0.17	$ 0.18	$ 0.15	$ 0.77	$ 0.59	$ 0.56
Diluted earnings per common share
Net income allocated to common shareholders (numerator)									$ 81,441	$ 62,718	$ 52,477
Weighted Average Shares Outstanding									105,143	105,880	92,955
Incremental shares from assumed exercise of outstanding options									80	246	101
Diluted Weighted Average Shares Outstanding (denominator)									105,223	106,126	93,056
Diluted earnings per common share	$ 0.21	$ 0.21	$ 0.20	$ 0.16	$ 0.09	$ 0.17	$ 0.18	$ 0.15	$ 0.77	$ 0.59	$ 0.56