Condensed Financial Information of Parent Company (Schedule of Condensed Statement of Income) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income from subsidiary:
Net interest income after provision									$ 38,245	$ 40,385	$ 43,711
Gain on sales of investment securities									4,024	2,635	43
Total income									114,817	111,523	106,535
Expenses [Abstract]
Salaries and employee benefits									65,722	62,563	56,573
Other expenses									1,347	1,080	1,849
Total operating expense	21,296	21,384	21,017	20,389	19,823	19,929	20,240	20,341	84,086	80,333	75,029
Income tax expense	1,582	1,533	2,106	2,013	1,607	1,890	2,205	2,185	7,234	7,887	8,497
Net income	5,254	6,138	6,073	6,032	5,341	6,092	5,962	5,908	23,497	23,303	23,009
Parent Company [Member]
Income from subsidiary:
Interest									12	24	18
Management fees									2,119	1,955	1,794
Income from subsidiary									2,131	1,979	1,812
Information services revenue									70,503	66,417	60,688
Net interest income after provision									15,069	17,563	19,933
Gain on sales of investment securities									3,677	3,145	43
Other income									527	535	701
Total income									91,907	89,639	83,177
Expenses [Abstract]
Salaries and employee benefits									59,004	55,981	50,296
Other expenses									15,027	14,492	14,462
Total operating expense									74,031	70,473	64,758
Income before income tax and equity in undistributed income of subsidiary									17,876	19,166	18,419
Income tax expense									2,381	2,914	3,156
Income before undistributed income of subsidiary									15,495	16,252	15,263
Equity in undistributed income of subsidiary									7,530	7,523	7,746
Intercompany elimination									472	(472)
Net income									$ 23,497	$ 23,303	$ 23,009