Impaired Loans (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Summary of the impaired loans by portfolio class of loans
Loans with a Specific Valuation Allowance, Recorded Balance	$ 45,688	$ 61,503
Loans with a Specific Valuation Allowance, Unpaid Principal Balance	48,477	63,406
Specific valuation allowance	11,597	11,949
Loans with a Specific Valuation Allowance, Average Balance	53,339	59,823
Loans without a Specific Valuation Allowance, Recorded Balance	115,678	138,177
Loans without a Specific Valuation Allowance, Unpaid Principal Balance	145,038	169,082
Loans without a Specific Valuation Allowance, Average Balance	128,645	139,129
Recorded balance	161,366	199,680
Unpaid principal balance	193,515	232,488
Average balance	181,984	198,952
Residential Real Estate
Summary of the impaired loans by portfolio class of loans
Loans with a Specific Valuation Allowance, Recorded Balance	4,110	7,233
Loans with a Specific Valuation Allowance, Unpaid Principal Balance	4,276	7,394
Specific valuation allowance	853	990
Loans with a Specific Valuation Allowance, Average Balance	5,480	7,237
Loans without a Specific Valuation Allowance, Recorded Balance	15,466	16,837
Loans without a Specific Valuation Allowance, Unpaid Principal Balance	16,683	18,033
Loans without a Specific Valuation Allowance, Average Balance	15,580	18,103
Recorded balance	19,576	24,070
Unpaid principal balance	20,959	25,427
Average balance	21,060	25,340
Commercial Real Estate
Summary of the impaired loans by portfolio class of loans
Loans with a Specific Valuation Allowance, Recorded Balance	27,155	23,917
Loans with a Specific Valuation Allowance, Unpaid Principal Balance	28,048	25,331
Specific valuation allowance	2,967	3,763
Loans with a Specific Valuation Allowance, Average Balance	24,519	26,105
Loans without a Specific Valuation Allowance, Recorded Balance	78,109	95,609
Loans without a Specific Valuation Allowance, Unpaid Principal Balance	100,266	119,017
Loans without a Specific Valuation Allowance, Average Balance	89,015	95,808
Recorded balance	105,264	119,526
Unpaid principal balance	128,314	144,348
Average balance	113,534	121,913
Other Commercial
Summary of the impaired loans by portfolio class of loans
Loans with a Specific Valuation Allowance, Recorded Balance	11,377	27,015
Loans with a Specific Valuation Allowance, Unpaid Principal Balance	12,461	27,238
Specific valuation allowance	6,836	6,155
Loans with a Specific Valuation Allowance, Average Balance	19,874	22,460
Loans without a Specific Valuation Allowance, Recorded Balance	13,944	14,489
Loans without a Specific Valuation Allowance, Unpaid Principal Balance	19,117	19,156
Loans without a Specific Valuation Allowance, Average Balance	14,024	14,106
Recorded balance	25,321	41,504
Unpaid principal balance	31,578	46,394
Average balance	33,898	36,566
Home Equity
Summary of the impaired loans by portfolio class of loans
Loans with a Specific Valuation Allowance, Recorded Balance	1,214	886
Loans with a Specific Valuation Allowance, Unpaid Principal Balance	1,336	949
Specific valuation allowance	447	265
Loans with a Specific Valuation Allowance, Average Balance	1,039	767
Loans without a Specific Valuation Allowance, Recorded Balance	5,687	8,153
Loans without a Specific Valuation Allowance, Unpaid Principal Balance	6,403	9,631
Loans without a Specific Valuation Allowance, Average Balance	7,163	8,844
Recorded balance	6,901	9,039
Unpaid principal balance	7,739	10,580
Average balance	8,202	9,611
Other Consumer
Summary of the impaired loans by portfolio class of loans
Loans with a Specific Valuation Allowance, Recorded Balance	1,832	2,452
Loans with a Specific Valuation Allowance, Unpaid Principal Balance	2,356	2,494
Specific valuation allowance	494	776
Loans with a Specific Valuation Allowance, Average Balance	2,427	3,254
Loans without a Specific Valuation Allowance, Recorded Balance	2,472	3,089
Loans without a Specific Valuation Allowance, Unpaid Principal Balance	2,569	3,245
Loans without a Specific Valuation Allowance, Average Balance	2,863	2,268
Recorded balance	4,304	5,541
Unpaid principal balance	4,925	5,739
Average balance	$ 5,290	$ 5,522