Earnings Per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Basic EPS
Net income	$ 60,069	$ 47,704	$ 31,428
Amount allocable to common shareholders	100.00%	100.00%	90.50%
Net income applicable to common stock	60,069	47,704	28,427
Basic weighted average shares outstanding	36,516	37,006	33,159
Basic earnings per share	$ 1.65	$ 1.29	$ 0.86
Diluted EPS
Net income	$ 60,069	$ 47,704	$ 31,428
Basic weighted average shares outstanding	36,516	37,006	33,159
Effect of dilutive shares:
Stock options, restricted stock and warrants	1,300	2,602	2,392
Diluted weighted average shares outstanding	37,816	39,608	39,051
Diluted earnings per share	$ 1.59	$ 1.20	$ 0.80
Common Stock Voting [Member]
Basic EPS
Basic weighted average shares outstanding	36,101	34,420	30,573
Diluted EPS
Basic weighted average shares outstanding	36,101	34,420	30,573
Common Stock Non-Voting [Member]
Basic EPS
Basic weighted average shares outstanding	415	2,586	2,586
Diluted EPS
Basic weighted average shares outstanding	415	2,586	2,586
Series B Preferred Stock [Member]
Effect of dilutive shares:
Series B Preferred Stock	0	0	3,500