Impaired Loans (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2015	Sep. 30, 2015	Dec. 31, 2014
Summary of the impaired loans by portfolio class of loans
Loans with a specific valuation allowance, Recorded balance	$ 32,176	$ 32,176	$ 45,688
Loans with a specific valuation allowance, Unpaid principal balance	32,931	32,931	48,477
Specific valuation allowance	7,497	7,497	11,597
Loans with a specific valuation allowance, Average balance	33,095	36,549	53,339
Loans without a specific valuation allowance, Recorded balance	114,063	114,063	115,678
Loans without a specific valuation allowance, Unpaid principal balance	140,979	140,979	145,038
Loans without a specific valuation allowance, Average balance	115,891	118,921	128,645
Recorded balance	146,239	146,239	161,366
Unpaid principal balance	173,910	173,910	193,515
Average balance	148,986	155,470	181,984
Residential Real Estate
Summary of the impaired loans by portfolio class of loans
Loans with a specific valuation allowance, Recorded balance	9,438	9,438	4,110
Loans with a specific valuation allowance, Unpaid principal balance	9,580	9,580	4,276
Specific valuation allowance	1,857	1,857	853
Loans with a specific valuation allowance, Average balance	7,246	5,927	5,480
Loans without a specific valuation allowance, Recorded balance	13,045	13,045	15,466
Loans without a specific valuation allowance, Unpaid principal balance	14,389	14,389	16,683
Loans without a specific valuation allowance, Average balance	13,095	13,890	15,580
Recorded balance	22,483	22,483	19,576
Unpaid principal balance	23,969	23,969	20,959
Average balance	20,341	19,817	21,060
Commercial Real Estate
Summary of the impaired loans by portfolio class of loans
Loans with a specific valuation allowance, Recorded balance	11,360	11,360	27,155
Loans with a specific valuation allowance, Unpaid principal balance	11,384	11,384	28,048
Specific valuation allowance	1,224	1,224	2,967
Loans with a specific valuation allowance, Average balance	13,236	16,646	24,519
Loans without a specific valuation allowance, Recorded balance	76,762	76,762	78,109
Loans without a specific valuation allowance, Unpaid principal balance	97,633	97,633	100,266
Loans without a specific valuation allowance, Average balance	78,255	80,032	89,015
Recorded balance	88,122	88,122	105,264
Unpaid principal balance	109,017	109,017	128,314
Average balance	91,491	96,678	113,534
Other Commercial
Summary of the impaired loans by portfolio class of loans
Loans with a specific valuation allowance, Recorded balance	9,532	9,532	11,377
Loans with a specific valuation allowance, Unpaid principal balance	9,613	9,613	12,461
Specific valuation allowance	3,956	3,956	6,836
Loans with a specific valuation allowance, Average balance	10,697	11,729	19,874
Loans without a specific valuation allowance, Recorded balance	14,811	14,811	13,944
Loans without a specific valuation allowance, Unpaid principal balance	18,469	18,469	19,117
Loans without a specific valuation allowance, Average balance	15,505	16,361	14,024
Recorded balance	24,343	24,343	25,321
Unpaid principal balance	28,082	28,082	31,578
Average balance	26,202	28,090	33,898
Home Equity
Summary of the impaired loans by portfolio class of loans
Loans with a specific valuation allowance, Recorded balance	175	175	1,214
Loans with a specific valuation allowance, Unpaid principal balance	195	195	1,336
Specific valuation allowance	52	52	447
Loans with a specific valuation allowance, Average balance	205	507	1,039
Loans without a specific valuation allowance, Recorded balance	7,230	7,230	5,687
Loans without a specific valuation allowance, Unpaid principal balance	8,209	8,209	6,403
Loans without a specific valuation allowance, Average balance	6,788	6,339	7,163
Recorded balance	7,405	7,405	6,901
Unpaid principal balance	8,404	8,404	7,739
Average balance	6,993	6,846	8,202
Other Consumer
Summary of the impaired loans by portfolio class of loans
Loans with a specific valuation allowance, Recorded balance	1,671	1,671	1,832
Loans with a specific valuation allowance, Unpaid principal balance	2,159	2,159	2,356
Specific valuation allowance	408	408	494
Loans with a specific valuation allowance, Average balance	1,711	1,740	2,427
Loans without a specific valuation allowance, Recorded balance	2,215	2,215	2,472
Loans without a specific valuation allowance, Unpaid principal balance	2,279	2,279	2,569
Loans without a specific valuation allowance, Average balance	2,248	2,299	2,863
Recorded balance	3,886	3,886	4,304
Unpaid principal balance	4,438	4,438	4,925
Average balance	$ 3,959	$ 4,039	$ 5,290