Condensed Financial Information of Parent Company (Schedule of Condensed Statement of Income) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income from subsidiaries:
Net interest income after provision									$ 39,401	$ 37,449	$ 37,299
Gain on sales of investment securities									387	2,910	23
Total net revenue									125,537	120,817	117,206
Expenses:
Salaries and employee benefits									72,581	70,314	66,100
Other expenses									1,913	1,185	1,647
Total operating expense	$ 23,946	$ 23,552	$ 23,059	$ 22,916	$ 22,201	$ 22,634	$ 22,640	$ 22,308	93,473	89,783	85,414
Income tax expense	1,806	1,855	2,035	2,020	2,017	2,083	1,932	1,946	7,716	7,978	7,759
Net income	$ 6,424	$ 6,222	$ 5,869	$ 5,833	$ 6,089	$ 5,880	$ 5,548	$ 5,539	24,348	23,056	24,033
Parent Company [Member]
Income from subsidiaries:
Interest									2	12	12
Management fees									2,105	2,201	2,058
Income from subsidiaries									2,107	2,213	2,070
Information services revenue									83,543	78,488	77,064
Net interest income after provision									13,389	13,948	14,986
Gain on sales of investment securities									387	2,910	23
Other income									504	613	1,323
Total net revenue									99,930	98,172	95,466
Expenses:
Salaries and employee benefits									65,968	63,475	59,885
Other expenses									18,133	16,580	15,587
Total operating expense									84,101	80,055	75,472
Income before income tax and equity in undistributed income of subsidiaries									15,829	18,117	19,994
Income tax expense									1,540	2,950	3,125
Income before undistributed income of subsidiaries									14,289	15,167	16,869
Equity in undistributed income of subsidiaries									10,059	7,889	7,164
Net income									$ 24,348	$ 23,056	$ 24,033