Impaired Loans (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2016	Dec. 31, 2015
Summary of the impaired loans by portfolio class of loans
Loans with a specific valuation allowance, Recorded balance	$ 31,631	$ 34,683
Loans with a specific valuation allowance, Unpaid principal balance	32,794	36,157
Specific valuation allowance	8,440	8,124
Loans with a specific valuation allowance, Average balance	33,157	36,176
Loans without a specific valuation allowance, Recorded balance	109,235	106,090
Loans without a specific valuation allowance, Unpaid principal balance	136,388	132,718
Loans without a specific valuation allowance, Average balance	107,662	116,356
Recorded balance	140,866	140,773
Unpaid principal balance	169,182	168,875
Average balance	140,819	152,532
Residential Real Estate
Summary of the impaired loans by portfolio class of loans
Loans with a specific valuation allowance, Recorded balance	7,501	8,253
Loans with a specific valuation allowance, Unpaid principal balance	8,364	9,198
Specific valuation allowance	597	782
Loans with a specific valuation allowance, Average balance	7,877	6,393
Loans without a specific valuation allowance, Recorded balance	13,540	12,514
Loans without a specific valuation allowance, Unpaid principal balance	15,042	13,969
Loans without a specific valuation allowance, Average balance	13,027	13,615
Recorded balance	21,041	20,767
Unpaid principal balance	23,406	23,167
Average balance	20,904	20,008
Commercial Real Estate
Summary of the impaired loans by portfolio class of loans
Loans with a specific valuation allowance, Recorded balance	10,077	12,554
Loans with a specific valuation allowance, Unpaid principal balance	10,094	12,581
Specific valuation allowance	914	1,629
Loans with a specific valuation allowance, Average balance	11,316	15,827
Loans without a specific valuation allowance, Recorded balance	71,763	73,291
Loans without a specific valuation allowance, Unpaid principal balance	92,608	94,028
Loans without a specific valuation allowance, Average balance	72,527	78,684
Recorded balance	81,840	85,845
Unpaid principal balance	102,702	106,609
Average balance	83,843	94,511
Other Commercial
Summary of the impaired loans by portfolio class of loans
Loans with a specific valuation allowance, Recorded balance	12,150	11,923
Loans with a specific valuation allowance, Unpaid principal balance	12,266	12,335
Specific valuation allowance	6,442	5,277
Loans with a specific valuation allowance, Average balance	12,036	11,768
Loans without a specific valuation allowance, Recorded balance	15,739	11,951
Loans without a specific valuation allowance, Unpaid principal balance	19,657	15,539
Loans without a specific valuation allowance, Average balance	13,845	15,479
Recorded balance	27,889	23,874
Unpaid principal balance	31,923	27,874
Average balance	25,881	27,247
Home Equity
Summary of the impaired loans by portfolio class of loans
Loans with a specific valuation allowance, Recorded balance	456	102
Loans with a specific valuation allowance, Unpaid principal balance	590	109
Specific valuation allowance	190	64
Loans with a specific valuation allowance, Average balance	279	426
Loans without a specific valuation allowance, Recorded balance	6,101	6,391
Loans without a specific valuation allowance, Unpaid principal balance	6,882	7,153
Loans without a specific valuation allowance, Average balance	6,246	6,350
Recorded balance	6,557	6,493
Unpaid principal balance	7,472	7,262
Average balance	6,525	6,776
Other Consumer
Summary of the impaired loans by portfolio class of loans
Loans with a specific valuation allowance, Recorded balance	1,447	1,851
Loans with a specific valuation allowance, Unpaid principal balance	1,480	1,934
Specific valuation allowance	297	372
Loans with a specific valuation allowance, Average balance	1,649	1,762
Loans without a specific valuation allowance, Recorded balance	2,092	1,943
Loans without a specific valuation allowance, Unpaid principal balance	2,199	2,029
Loans without a specific valuation allowance, Average balance	2,017	2,228
Recorded balance	3,539	3,794
Unpaid principal balance	3,679	3,963
Average balance	$ 3,666	$ 3,990