Allowance for Loan Losses Allowance Rollforward (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and Leases Receivable, Allowance at Beginning of Period	$ 74,742	$ 78,077
Financing Receivable, Allowance for Credit Losses, Charge-offs	(389)	(58)
Financing Receivable, Allowance for Credit Losses, Recoveries	340	193
Provision/ (credit) for loan losses	(1,795)	(181)
Loans and Leases Receivable, Allowance at End of Period	72,898	78,031
Commercial and Industrial Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and Leases Receivable, Allowance at Beginning of Period	11,735	12,751
Financing Receivable, Allowance for Credit Losses, Charge-offs	(214)	0
Financing Receivable, Allowance for Credit Losses, Recoveries	82	87
Provision/ (credit) for loan losses	(160)	(547)
Loans and Leases Receivable, Allowance at End of Period	11,443	12,291
Commercial real estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and Leases Receivable, Allowance at Beginning of Period	46,820	50,412
Financing Receivable, Allowance for Credit Losses, Charge-offs	(135)	0
Financing Receivable, Allowance for Credit Losses, Recoveries	125	50
Provision/ (credit) for loan losses	(694)	702
Loans and Leases Receivable, Allowance at End of Period	46,116	51,164
Construction and land [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and Leases Receivable, Allowance at Beginning of Period	4,949	3,039
Financing Receivable, Allowance for Credit Losses, Charge-offs	0	0
Financing Receivable, Allowance for Credit Losses, Recoveries	0	0
Provision/ (credit) for loan losses	(416)	158
Loans and Leases Receivable, Allowance at End of Period	4,533	3,197
Residential [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and Leases Receivable, Allowance at Beginning of Period	9,773	10,449
Financing Receivable, Allowance for Credit Losses, Charge-offs	(16)	(58)
Financing Receivable, Allowance for Credit Losses, Recoveries	0	47
Provision/ (credit) for loan losses	139	(348)
Loans and Leases Receivable, Allowance at End of Period	9,896	10,090
Home equity [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and Leases Receivable, Allowance at Beginning of Period	835	1,035
Financing Receivable, Allowance for Credit Losses, Charge-offs	0	0
Financing Receivable, Allowance for Credit Losses, Recoveries	1	0
Provision/ (credit) for loan losses	(52)	(48)
Loans and Leases Receivable, Allowance at End of Period	784	987
Consumer and other [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and Leases Receivable, Allowance at Beginning of Period	630	391
Financing Receivable, Allowance for Credit Losses, Charge-offs	(24)	0
Financing Receivable, Allowance for Credit Losses, Recoveries	132	9
Provision/ (credit) for loan losses	(612)	(98)
Loans and Leases Receivable, Allowance at End of Period	$ 126	$ 302