Loans Receivable and Credit Quality Nonaccrual Loans by Class of Financing Receivable (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	$ 17,315	$ 26,571
Commercial and Industrial Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	572	1,019
Commercial Loan [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	572	1,019
Commercial Tax Exempt [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	0	0
Commercial Real Estate Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	4,583	11,232
Construction Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	179	3,297
Residential Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	10,908	9,661
Home Equity Line of Credit [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	1,072	1,306
Consumer Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	$ 1	$ 56