Loans, Allowance for Loan Losses and Credit Quality (Summary of Nonaccrual Loans) (Details) - USD ($) $ in Thousands		Mar. 31, 2018	Dec. 31, 2017
Financing Receivable Impaired [Line Items]
Tdrs Recorded Investment On Nonaccrual Status		$ 5,637	$ 6,067
Financing Receivable, Recorded Investment, Nonaccrual Status	[1]	47,704	49,630
Commercial and Industrial [Member]
Financing Receivable Impaired [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status		30,751	32,055
Commercial Real Estate [Member]
Financing Receivable Impaired [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status		2,997	3,123
Small Business [Member]
Financing Receivable Impaired [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status		412	230
Residential Real Estate [Member]
Financing Receivable Impaired [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status		7,646	8,129
Consumer Home Equity [Member]
Financing Receivable Impaired [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status		5,858	6,022
Consumer - Other [Member]
Financing Receivable Impaired [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status		$ 40	$ 71

[1] (1)Included in these amounts were $5.6 million and $6.1 million of nonaccruing TDRs at March 31, 2018 and December 31, 2017, respectively.