Segment Reporting (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019 USD ($) item	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2019 USD ($) segment item	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Segment Reporting
Number of operating segments | segment									4
Number of Banking offices | item	15								15
Number of satellite offices | item									13
Key metrics related to segments
Net interest income	$ 18,459	$ 18,681	$ 18,291	$ 19,120	$ 19,253	$ 18,929	$ 18,900	$ 18,142	$ 74,551	$ 75,224	$ 67,670
Provision for loan losses	1,797	1,498	1,797	2,220	1,530	1,530	4,020	1,530	7,312	8,610	3,280
Noninterest income	29,556	29,580	29,984	25,074	26,141	26,258	26,094	24,256	114,194	102,749	103,045
Noninterest expense	36,435	37,327	35,261	33,514	35,911	34,336	33,808	32,270	142,537	136,325	134,920
Net income before taxes	9,783	$ 9,436	$ 11,217	$ 8,460	7,953	$ 9,321	$ 7,166	$ 8,598	38,896	33,038	32,515
Total assets	2,356,878				2,179,070				2,356,878	2,179,070	2,136,081
Corporate Administration
Key metrics related to segments
Net interest income									(3,610)	(3,591)	(3,504)
Noninterest income									2,106	(18)	(226)
Noninterest expense									34,894	33,283	31,859
Net income before taxes									(36,398)	(36,892)	(35,589)
Total assets	10,412				(506)				10,412	(506)	(1,437)
Banking | Operating Segments
Key metrics related to segments
Net interest income									76,916	77,919	70,377
Provision for loan losses									7,312	8,599	3,280
Noninterest income									6,970	6,921	7,180
Noninterest expense									43,171	42,605	35,996
Net income before taxes									33,403	33,636	38,281
Total assets	2,259,614				2,120,249				2,259,614	2,120,249	2,078,013
Retirement and Benefit Services | Operating Segments
Key metrics related to segments
Noninterest income									63,811	63,316	62,390
Noninterest expense									35,407	36,414	41,977
Net income before taxes									28,404	26,902	20,413
Total assets	39,021				41,492				39,021	41,492	38,118
Wealth Management | Operating Segments
Key metrics related to segments
Net interest income										62	57
Noninterest income									15,502	14,900	13,953
Noninterest expense									7,188	6,824	7,640
Net income before taxes									8,314	8,138	6,370
Total assets	128				3,235				128	3,235	2,718
Mortgage | Operating Segments
Key metrics related to segments
Net interest income									1,245	834	740
Provision for loan losses										11
Noninterest income									25,805	17,630	19,748
Noninterest expense									21,877	17,199	17,448
Net income before taxes									5,173	1,254	3,040
Total assets	$ 47,703				$ 14,600				$ 47,703	$ 14,600	$ 18,669