Business Segments (Statement of Operations and Total Assets by Reportable Segment) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020		Dec. 31, 2019		Dec. 31, 2018
Segment Reporting Information [Line Items]
Net interest income (expense)	$ 32,243	$ 31,654	$ 30,945	$ 32,602	$ 31,994	$ 32,978	$ 33,858	$ 34,584	$ 127,444	[1]	$ 133,414	[1]	$ 132,290	[1]
Provision for credit losses	1,781	1,325	2,200	7,036	0	400	525	650	12,342		1,575		1,550
Net interest income after provision for credit losses	30,462	30,329	28,745	25,566	31,994	32,578	33,333	33,934	115,102		131,839		130,740
Noninterest income	27,727	25,468	26,320	19,927	16,618	18,342	16,753	15,367	99,442	[1]	67,080	[1]	62,114	[1]
Depreciation and amortization expense									4,090		4,234		4,261
Other noninterest expenses									121,294		106,506		101,901
Noninterest expense	34,109	32,344	28,478	30,453	28,755	26,870	28,151	26,964	125,384		110,740		106,162
Income before income taxes	24,080	23,453	26,587	15,040	19,857	24,050	21,935	22,337	89,160		88,179		86,692
Income tax expense	5,514	5,131	5,547	3,139	4,321	5,236	4,662	4,842	19,331		19,061		18,260
Net income	18,566	$ 18,322	$ 21,040	$ 11,901	15,536	$ 18,814	$ 17,273	$ 17,495	69,829		69,118		68,432
Total assets	5,713,169				5,292,659				5,713,169		5,292,659		5,010,766
Expenditures for long-lived assets									3,406		3,132		3,974
Commercial Banking [Member]
Segment Reporting Information [Line Items]
Net interest income (expense)									128,600		112,414		106,668
Provision for credit losses									12,342		1,575		1,550
Net interest income after provision for credit losses									116,258		110,839		105,118
Noninterest income									61,463		27,857		21,509
Depreciation and amortization expense									2,512		2,630		2,589
Other noninterest expenses									77,157		66,517		62,673
Noninterest expense									79,669		69,147		65,262
Income before income taxes									98,052		69,549		61,365
Income tax expense									21,216		15,189		13,149
Net income									76,836		54,360		48,216
Total assets	4,501,875				4,070,594				4,501,875		4,070,594		3,804,021
Expenditures for long-lived assets									3,097		2,521		3,415
Wealth Management Services [Member]
Segment Reporting Information [Line Items]
Net interest income (expense)									(141)		(438)		(334)
Provision for credit losses									0		0		0
Net interest income after provision for credit losses									(141)		(438)		(334)
Noninterest income									35,454		36,856		38,341
Depreciation and amortization expense									1,412		1,445		1,501
Other noninterest expenses									27,367		26,057		26,222
Noninterest expense									28,779		27,502		27,723
Income before income taxes									6,534		8,916		10,284
Income tax expense									1,746		2,308		2,577
Net income									4,788		6,608		7,707
Total assets	74,958				74,990				74,958		74,990		71,254
Expenditures for long-lived assets									158		445		407
Corporate [Member]
Segment Reporting Information [Line Items]
Net interest income (expense)									(1,015)		21,438		25,956
Provision for credit losses									0		0		0
Net interest income after provision for credit losses									(1,015)		21,438		25,956
Noninterest income									2,525		2,367		2,264
Depreciation and amortization expense									166		159		171
Other noninterest expenses									16,770		13,932		13,006
Noninterest expense									16,936		14,091		13,177
Income before income taxes									(15,426)		9,714		15,043
Income tax expense									(3,631)		1,564		2,534
Net income									(11,795)		8,150		12,509
Total assets	$ 1,136,336				$ 1,147,075				1,136,336		1,147,075		1,135,491
Expenditures for long-lived assets									$ 151		$ 166		$ 152

[1] As reported in the Consolidated Statements of Income.