Parent-Only Financial Information (Selected Quarterly Financial Data (Unaudited)) (Details) (USD $) In Thousands, except Per Share data, 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
Selected Operating Data:
Interest income									$ 91,701	$ 92,470	$ 91,539
Interest expense									15,352	16,948	22,644
Net interest income									76,349	75,522	68,895
Provision for loan losses									645	1,927	3,536
Net interest income after provision for loan losses									75,704	73,595	65,359
Other income									8,460	10,161	8,586
Other expenses									52,042	53,873	48,998
Income before income tax expense									32,122	29,883	24,947
Income tax expense									11,856	10,736	8,916
Net income									20,266	19,147	16,031
Net income per common share-basic									$ 0.41	$ 0.35	$ 0.30
Net income per common share-diluted									$ 0.41	$ 0.34	$ 0.29
Parent Company
Selected Operating Data:
Interest income	24,079	22,707	22,151	22,764	22,620	23,380	22,954	23,516
Interest expense	4,335	3,737	3,631	3,649	3,938	4,060	4,199	4,751
Net interest income	19,744	18,970	18,520	19,115	18,682	19,320	18,755	18,765
Provision for loan losses	57	317	(146)	417	416	817	417	277
Net interest income after provision for loan losses	19,687	18,653	18,666	18,698	18,266	18,503	18,338	18,488
Other income	2,061	1,840	2,387	2,172	2,619	2,588	1,698	3,256
Other expenses	14,013	13,268	12,698	12,063	12,989	13,309	13,209	14,366
Income before income tax expense	7,735	7,225	8,355	8,807	7,896	7,782	6,827	7,378
Income tax expense	2,857	2,496	2,915	3,588	2,940	2,682	2,528	2,586	261	25	(255)
Net income	$ 4,878	$ 4,729	$ 5,440	$ 5,219	$ 4,956	$ 5,100	$ 4,299	$ 4,792	$ 20,266	$ 19,147	$ 16,031
Net income per common share-basic	$ 0.11	$ 0.10	$ 0.11	$ 0.10	$ 0.09	$ 0.09	$ 0.08	$ 0.09
Net income per common share-diluted	$ 0.11	$ 0.10	$ 0.11	$ 0.10	$ 0.09	$ 0.09	$ 0.08	$ 0.09