Operating Expenses (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Operating Expenses [Abstract]
Salaries and wages									$ 84,807	$ 78,014	$ 68,668
Employee benefits									19,411	18,405	15,715
Occupancy									15,842	13,934	12,413
Equipment and software									15,297	13,734	13,112
Outside processing/service fees									12,372	11,134	10,679
FDIC insurance premiums									4,307	4,362	4,320
Professional fees									6,125	3,771	4,347
Postage and express mail									3,557	3,051	3,149
Advertising and marketing									3,449	2,971	3,106
Donations									1,155	2,829	1,892
Training, travel and other employee expenses									2,748	2,512	2,530
Telephone									1,966	1,940	1,693
Intangible asset amortization									2,029	1,909	1,569
Supplies									1,897	1,670	1,567
Credit-related expenses									996	707	3,816
Other									3,967	4,005	3,345
Total Operating Expenses	$ 52,616	$ 42,702	$ 42,425	$ 42,182	$ 42,405	$ 39,545	$ 41,041	$ 41,957	$ 179,925	$ 164,948	$ 151,921