Business Segments (Statement of Operations and Total Assets by Reportable Segment) (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
Segment Reporting Information [Line Items]
Net interest income (expense)	$ 28,588	$ 27,379	$ 26,776	$ 27,735	$ 26,255	$ 25,997	$ 26,028	$ 25,702	$ 110,478	$ 103,982	$ 99,505
Provision for loan losses	2,900	1,800	450	500	750	200	100	0	5,650	1,050	1,850
Net interest income after provision for loan losses	25,688	25,579	26,326	27,235	25,505	25,797	25,928	25,702	104,828	102,932	97,655
Noninterest income	17,320	17,261	15,914	14,634	15,146	13,913	15,261	14,020	65,129	58,340	59,015
Depreciation and amortization expense									4,935	4,285	3,777
Other noninterest expenses									96,168	92,644	93,070
Total noninterest expense	24,973	24,650	26,030	25,450	24,561	24,538	24,299	23,531	101,103	96,929	96,847
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 expense (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
Total assets at period end	4,381,115				3,771,604				4,381,115	3,771,604	3,586,874
Expenditures for long-lived assets									3,112	5,479	5,226
Commercial Banking [Member]
Segment Reporting Information [Line Items]
Net interest income (expense)									91,221	84,757	80,500
Provision for loan losses									5,650	1,050	1,850
Net interest income after provision for loan losses									85,571	83,707	78,650
Noninterest income									24,783	20,618	17,575
Depreciation and amortization expense									2,771	2,584	2,447
Other noninterest expenses									58,452	55,203	52,639
Total noninterest expense									61,223	57,787	55,086
Income before income taxes									49,131	46,538	41,139
Income tax expense (benefit)									16,790	15,330	13,497
Net income									32,341	31,208	27,642
Total assets at period end	3,354,633				3,152,231				3,354,633	3,152,231	2,986,453
Expenditures for long-lived assets									2,267	4,714	3,474
Wealth Management Services [Member]
Segment Reporting Information [Line Items]
Net interest income (expense)									(66)	(47)	(24)
Provision for loan losses									0	0	0
Net interest income after provision for loan losses									(66)	(47)	(24)
Noninterest income									37,569	35,416	33,378
Depreciation and amortization expense									1,940	1,488	1,127
Other noninterest expenses									25,239	25,632	22,386
Total noninterest expense									27,179	27,120	23,513
Income before income taxes									10,324	8,249	9,841
Income tax expense (benefit)									3,692	3,475	3,724
Net income									6,632	4,774	6,117
Total assets at period end	64,625				63,801				64,625	63,801	52,720
Expenditures for long-lived assets									464	411	1,578
Corporate [Member]
Segment Reporting Information [Line Items]
Net interest income (expense)									19,323	19,272	19,029
Provision for loan losses									0	0	0
Net interest income after provision for loan losses									19,323	19,272	19,029
Noninterest income									2,777	2,306	8,062
Depreciation and amortization expense									224	213	203
Other noninterest expenses									12,477	11,809	18,045
Total noninterest expense									12,701	12,022	18,248
Income before income taxes									9,399	9,556	8,843
Income tax expense (benefit)									1,891	2,073	1,778
Net income									7,508	7,483	7,065
Total assets at period end	$ 961,857				$ 555,572				961,857	555,572	547,701
Expenditures for long-lived assets									$ 381	$ 354	$ 174