Impaired Loans (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2013	Sep. 30, 2013	Dec. 31, 2012
Summary of the impaired loans by portfolio class of loans
Loans with a specific valuation allowance, Recorded balance	$ 62,614	$ 62,614	$ 62,759
Loans with a specific valuation allowance, Unpaid principal balance	64,969	64,969	70,261
Loans with a specific valuation allowance, Specific valuation allowance	12,728	12,728	15,534
Loans with a specific valuation allowance, Average balance	59,817	59,402	76,656
Loans without a specific valuation allowance, Recorded balance	144,304	144,304	138,976
Loans without a specific valuation allowance, Unpaid principal balance	174,258	174,258	149,412
Loans without a specific valuation allowance, Average balance	139,928	139,368	162,505
Recorded balance	206,918	206,918	201,735
Unpaid principal balance	239,227	239,227	219,673
Specific valuation allowance	12,728	12,728	15,534
Average balance	199,745	198,770	239,161
Residential Real Estate
Summary of the impaired loans by portfolio class of loans
Loans with a specific valuation allowance, Recorded balance	7,887	7,887	7,334
Loans with a specific valuation allowance, Unpaid principal balance	8,032	8,032	7,459
Loans with a specific valuation allowance, Specific valuation allowance	1,088	1,088	1,680
Loans with a specific valuation allowance, Average balance	7,431	7,237	12,797
Loans without a specific valuation allowance, Recorded balance	19,217	19,217	18,528
Loans without a specific valuation allowance, Unpaid principal balance	20,681	20,681	19,613
Loans without a specific valuation allowance, Average balance	18,481	18,420	16,034
Recorded balance	27,104	27,104	25,862
Unpaid principal balance	28,713	28,713	27,072
Specific valuation allowance	1,088	1,088	1,680
Average balance	25,912	25,657	28,831
Commercial Real Estate
Summary of the impaired loans by portfolio class of loans
Loans with a specific valuation allowance, Recorded balance	28,194	28,194	29,595
Loans with a specific valuation allowance, Unpaid principal balance	29,463	29,463	36,887
Loans with a specific valuation allowance, Specific valuation allowance	6,662	6,662	7,716
Loans with a specific valuation allowance, Average balance	26,525	26,653	36,164
Loans without a specific valuation allowance, Recorded balance	97,372	97,372	95,687
Loans without a specific valuation allowance, Unpaid principal balance	120,914	120,914	102,798
Loans without a specific valuation allowance, Average balance	95,175	95,857	111,554
Recorded balance	125,566	125,566	125,282
Unpaid principal balance	150,377	150,377	139,685
Specific valuation allowance	6,662	6,662	7,716
Average balance	121,700	122,510	147,718
Other Commercial
Summary of the impaired loans by portfolio class of loans
Loans with a specific valuation allowance, Recorded balance	22,368	22,368	21,205
Loans with a specific valuation allowance, Unpaid principal balance	22,986	22,986	21,278
Loans with a specific valuation allowance, Specific valuation allowance	3,810	3,810	3,859
Loans with a specific valuation allowance, Average balance	21,780	21,321	22,665
Loans without a specific valuation allowance, Recorded balance	16,022	16,022	12,388
Loans without a specific valuation allowance, Unpaid principal balance	19,233	19,233	14,318
Loans without a specific valuation allowance, Average balance	15,768	14,011	19,733
Recorded balance	38,390	38,390	33,593
Unpaid principal balance	42,219	42,219	35,596
Specific valuation allowance	3,810	3,810	3,859
Average balance	37,548	35,332	42,398
Home Equity
Summary of the impaired loans by portfolio class of loans
Loans with a specific valuation allowance, Recorded balance	673	673	1,354
Loans with a specific valuation allowance, Unpaid principal balance	717	717	1,362
Loans with a specific valuation allowance, Specific valuation allowance	109	109	870
Loans with a specific valuation allowance, Average balance	495	737	1,390
Loans without a specific valuation allowance, Recorded balance	9,418	9,418	9,720
Loans without a specific valuation allowance, Unpaid principal balance	11,026	11,026	9,965
Loans without a specific valuation allowance, Average balance	8,766	9,017	11,993
Recorded balance	10,091	10,091	11,074
Unpaid principal balance	11,743	11,743	11,327
Specific valuation allowance	109	109	870
Average balance	9,261	9,754	13,383
Other Consumer
Summary of the impaired loans by portfolio class of loans
Loans with a specific valuation allowance, Recorded balance	3,492	3,492	3,271
Loans with a specific valuation allowance, Unpaid principal balance	3,771	3,771	3,275
Loans with a specific valuation allowance, Specific valuation allowance	1,059	1,059	1,409
Loans with a specific valuation allowance, Average balance	3,586	3,454	3,640
Loans without a specific valuation allowance, Recorded balance	2,275	2,275	2,653
Loans without a specific valuation allowance, Unpaid principal balance	2,404	2,404	2,718
Loans without a specific valuation allowance, Average balance	1,738	2,063	3,191
Recorded balance	5,767	5,767	5,924
Unpaid principal balance	6,175	6,175	5,993
Specific valuation allowance	1,059	1,059	1,409
Average balance	$ 5,324	$ 5,517	$ 6,831