Loans, Allowance for Credit Losses, and Credit Quality Loans Modified in a Troubled Debt Restructuring (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015 USD ($) loan	Sep. 30, 2014 USD ($) loan	Sep. 30, 2015 USD ($) loan	Sep. 30, 2014 USD ($) loan
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	67	103	156	203
Recorded Investment	$ 5,056	$ 18,504	$ 17,713	$ 26,373
Unpaid Principal Balance	$ 5,318	$ 19,168	$ 18,849	$ 27,599
Commercial and Industrial [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	5	10	10	13
Recorded Investment	$ 893	$ 7,383	$ 2,410	$ 7,695
Unpaid Principal Balance	$ 896	$ 7,384	$ 3,033	$ 7,707
Commercial Real Estate Owner Occupied [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	0	0	4	2
Recorded Investment	$ 0	$ 0	$ 2,847	$ 1,123
Unpaid Principal Balance	$ 0	$ 0	$ 3,007	$ 1,260
Commercial Real Estate Investor [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	2	3	3	4
Recorded Investment	$ 711	$ 5,603	$ 2,949	$ 6,096
Unpaid Principal Balance	$ 761	$ 5,918	$ 2,998	$ 6,425
Real Estate Construction [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	0	1	1	2
Recorded Investment	$ 0	$ 8	$ 5	$ 14
Unpaid Principal Balance	$ 0	$ 8	$ 5	$ 14
Home Equity Portfolio [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	27	38	61	85
Recorded Investment	$ 840	$ 1,121	$ 2,109	$ 2,784
Unpaid Principal Balance	$ 940	$ 1,179	$ 2,220	$ 2,970
Installment and Credit Cards [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | loan		2		3
Recorded Investment		$ 25		$ 34
Unpaid Principal Balance		$ 25		$ 45
Residential Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	33	49	77	94
Recorded Investment	$ 2,612	$ 4,364	$ 7,393	$ 8,627
Unpaid Principal Balance	$ 2,721	$ 4,654	$ 7,586	$ 9,178