Loans, Allowance for Credit Losses, and Credit Quality Loans Modified in a Troubled Debt Restructuring (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015 USD ($) loan	Jun. 30, 2014 USD ($) loan	Jun. 30, 2015 USD ($) loan	Jun. 30, 2014 USD ($) loan
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	59	69	114	130
Recorded Investment	$ 5,383	$ 5,014	$ 14,742	$ 17,415
Unpaid Principal Balance	$ 5,889	$ 5,608	$ 15,453	$ 22,733
Commercial and Industrial [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	4	3	6	11
Recorded Investment	$ 1,666	$ 526	$ 1,847	$ 3,889
Unpaid Principal Balance	$ 2,101	$ 534	$ 2,296	$ 7,736
Commercial Real Estate Owner Occupied [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	0	1	5	5
Recorded Investment	$ 0	$ 894	$ 3,506	$ 6,096
Unpaid Principal Balance	$ 0	$ 894	$ 3,636	$ 6,652
Commercial Real Estate Investor [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	0	0	1	1
Recorded Investment	$ 0	$ 0	$ 2,237	$ 493
Unpaid Principal Balance	$ 0	$ 0	$ 2,237	$ 508
Real Estate Construction [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	1	1	1	1
Recorded Investment	$ 6	$ 6	$ 6	$ 6
Unpaid Principal Balance	$ 6	$ 6	$ 6	$ 6
Home Equity Portfolio [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	26	35	49	62
Recorded Investment	$ 850	$ 1,630	$ 1,897	$ 2,476
Unpaid Principal Balance	$ 850	$ 1,723	$ 1,898	$ 2,693
Installment and Credit Cards [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | loan		1		2
Recorded Investment		$ 16		$ 25
Unpaid Principal Balance		$ 16		$ 35
Residential Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
Number of Loans | loan	28	28	52	48
Recorded Investment	$ 2,861	$ 1,942	$ 5,249	$ 4,430
Unpaid Principal Balance	$ 2,932	$ 2,435	$ 5,380	$ 5,103