Parent Company Financial Statements (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
Expenses:
Interest on junior subordinated debentures									$ 491	$ 871	$ 964
Legal and professional fees									2,579	2,741	2,336
Acquisition related expenses									0	989	0
Change in fair value of contingent consideration									(898)	41	0
Income before income taxes	$ 18,035	$ 18,190	$ 16,210	$ 16,419	$ 16,090	$ 15,172	$ 16,890	$ 16,191	68,854	64,343	59,823
Income tax benefit	(5,873)	(5,863)	(5,153)	(5,484)	(5,346)	(4,964)	(5,387)	(5,181)	(22,373)	(20,878)	(18,999)
Net income	$ 12,162	$ 12,327	$ 11,057	$ 10,935	$ 10,744	$ 10,208	$ 11,503	$ 11,010	46,481	43,465	40,824
Parent Company [Member]
Income:
Dividends from subsidiaries									24,542	23,399	20,116
Other income									15	13	13
Total income									24,557	23,412	20,129
Expenses:
Interest on junior subordinated debentures									491	871	964
Legal and professional fees									98	134	96
Acquisition related expenses									0	308	0
Change in fair value of contingent consideration									(898)	41	0
Other									282	254	253
Total expenses									(27)	1,608	1,313
Income before income taxes									24,584	21,804	18,816
Income tax benefit									(15)	557	454
Income before equity in undistributed earnings of subsidiaries									24,569	22,361	19,270
Equity in undistributed earnings of subsidiaries									21,912	21,104	21,554
Net income									$ 46,481	$ 43,465	$ 40,824