Earnings Per Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Computation of basic and diluted earnings per common share
Net income	$ 13,482	$ 13,444	$ 39,604	$ 36,161
Basic weighted average shares outstanding	36,500	37,126	36,521	36,798
Basic earnings per share	$ 0.37	$ 0.36	$ 1.08	$ 0.98
Effect of dilutive shares:
Stock options and restricted stock	1,041	439	1,371	403
Warrants		2,263		2,338
Diluted weighted average shares outstanding	37,541	39,828	37,892	39,539
Diluted earnings per share	$ 0.36	$ 0.34	$ 1.05	$ 0.91
Common Stock Voting [Member]
Computation of basic and diluted earnings per common share
Net income
Basic weighted average shares outstanding	36,500	34,540	35,968	34,212
Common Stock Non-Voting [Member]
Computation of basic and diluted earnings per common share
Net income
Basic weighted average shares outstanding		2,586	553	2,586