Impaired Loans (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2017	Dec. 31, 2016
Summary of the impaired loans by portfolio class of loans
Loans with a specific valuation allowance, Recorded balance	$ 17,940	$ 17,940	$ 22,128
Loans with a specific valuation allowance, Unpaid principal balance	18,432	18,432	22,374
Specific valuation allowance	4,077	4,077	6,881
Loans with a specific valuation allowance, Average balance	17,616	19,310	26,745
Loans without a specific valuation allowance, Recorded balance	104,953	104,953	108,135
Loans without a specific valuation allowance, Unpaid principal balance	129,250	129,250	131,059
Loans without a specific valuation allowance, Average balance	107,038	109,355	108,827
Recorded balance	122,893	122,893	130,263
Unpaid principal balance	147,682	147,682	153,433
Average balance	124,654	128,665	135,572
Residential Real Estate | Residential Real Estate
Summary of the impaired loans by portfolio class of loans
Loans with a specific valuation allowance, Recorded balance	3,121	3,121	2,759
Loans with a specific valuation allowance, Unpaid principal balance	3,272	3,272	2,825
Specific valuation allowance	320	320	856
Loans with a specific valuation allowance, Average balance	3,005	2,916	4,942
Loans without a specific valuation allowance, Recorded balance	10,289	10,289	8,853
Loans without a specific valuation allowance, Unpaid principal balance	11,151	11,151	9,925
Loans without a specific valuation allowance, Average balance	10,369	9,937	12,858
Recorded balance	13,410	13,410	11,612
Unpaid principal balance	14,423	14,423	12,750
Average balance	13,374	12,853	17,800
Commercial | Commercial Real Estate
Summary of the impaired loans by portfolio class of loans
Loans with a specific valuation allowance, Recorded balance	5,275	5,275	9,129
Loans with a specific valuation allowance, Unpaid principal balance	5,364	5,364	9,130
Specific valuation allowance	666	666	922
Loans with a specific valuation allowance, Average balance	5,151	6,177	10,441
Loans without a specific valuation allowance, Recorded balance	73,795	73,795	76,505
Loans without a specific valuation allowance, Unpaid principal balance	94,342	94,342	94,180
Loans without a specific valuation allowance, Average balance	76,233	77,286	72,323
Recorded balance	79,070	79,070	85,634
Unpaid principal balance	99,706	99,706	103,310
Average balance	81,384	83,463	82,764
Commercial | Other Commercial
Summary of the impaired loans by portfolio class of loans
Loans with a specific valuation allowance, Recorded balance	7,832	7,832	8,814
Loans with a specific valuation allowance, Unpaid principal balance	8,038	8,038	8,929
Specific valuation allowance	2,407	2,407	4,419
Loans with a specific valuation allowance, Average balance	7,667	8,550	9,840
Loans without a specific valuation allowance, Recorded balance	14,624	14,624	15,136
Loans without a specific valuation allowance, Unpaid principal balance	16,898	16,898	17,724
Loans without a specific valuation allowance, Average balance	14,332	15,199	15,537
Recorded balance	22,456	22,456	23,950
Unpaid principal balance	24,936	24,936	26,653
Average balance	21,999	23,749	25,377
Consumer and Other | Home Equity
Summary of the impaired loans by portfolio class of loans
Loans with a specific valuation allowance, Recorded balance	336	336	334
Loans with a specific valuation allowance, Unpaid principal balance	353	353	345
Specific valuation allowance	94	94	296
Loans with a specific valuation allowance, Average balance	363	402	257
Loans without a specific valuation allowance, Recorded balance	4,264	4,264	5,600
Loans without a specific valuation allowance, Unpaid principal balance	4,799	4,799	7,120
Loans without a specific valuation allowance, Average balance	4,300	5,026	6,004
Recorded balance	4,600	4,600	5,934
Unpaid principal balance	5,152	5,152	7,465
Average balance	4,663	5,428	6,261
Consumer and Other | Other Consumer
Summary of the impaired loans by portfolio class of loans
Loans with a specific valuation allowance, Recorded balance	1,376	1,376	1,092
Loans with a specific valuation allowance, Unpaid principal balance	1,405	1,405	1,145
Specific valuation allowance	590	590	388
Loans with a specific valuation allowance, Average balance	1,430	1,265	1,265
Loans without a specific valuation allowance, Recorded balance	1,981	1,981	2,041
Loans without a specific valuation allowance, Unpaid principal balance	2,060	2,060	2,110
Loans without a specific valuation allowance, Average balance	1,804	1,907	2,105
Recorded balance	3,357	3,357	3,133
Unpaid principal balance	3,465	3,465	3,255
Average balance	$ 3,234	$ 3,172	$ 3,370