Allowance for Loan Losses Allowance Rollforward (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and Leases Receivable, Allowance at Beginning of Period	$ 72,898	$ 78,031	$ 74,742	$ 78,077
Financing Receivable, Allowance for Credit Losses, Charge-offs	(140)	(463)	(529)	(521)
Financing Receivable, Allowance for Credit Losses, Recoveries	253	3,555	593	3,748
Provision/ (credit) for loan losses	453	(6,114)	(1,342)	(6,295)
Loans and Leases Receivable, Allowance at End of Period	73,464	75,009	73,464	75,009
Commercial and Industrial Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and Leases Receivable, Allowance at Beginning of Period	11,443	12,291	11,735	12,751
Financing Receivable, Allowance for Credit Losses, Charge-offs	(125)	(218)	(339)	(218)
Financing Receivable, Allowance for Credit Losses, Recoveries	152	67	234	154
Provision/ (credit) for loan losses	911	(468)	751	(1,015)
Loans and Leases Receivable, Allowance at End of Period	12,381	11,672	12,381	11,672
Commercial real estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and Leases Receivable, Allowance at Beginning of Period	46,116	51,164	46,820	50,412
Financing Receivable, Allowance for Credit Losses, Charge-offs	0	0	(135)	0
Financing Receivable, Allowance for Credit Losses, Recoveries	50	3,479	175	3,529
Provision/ (credit) for loan losses	(983)	(6,507)	(1,677)	(5,805)
Loans and Leases Receivable, Allowance at End of Period	45,183	48,136	45,183	48,136
Construction and land [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and Leases Receivable, Allowance at Beginning of Period	4,533	3,197	4,949	3,039
Financing Receivable, Allowance for Credit Losses, Charge-offs	0	0	0	0
Financing Receivable, Allowance for Credit Losses, Recoveries	0	0	0	0
Provision/ (credit) for loan losses	80	388	(336)	546
Loans and Leases Receivable, Allowance at End of Period	4,613	3,585	4,613	3,585
Residential [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and Leases Receivable, Allowance at Beginning of Period	9,896	10,090	9,773	10,449
Financing Receivable, Allowance for Credit Losses, Charge-offs	0	0	(16)	(58)
Financing Receivable, Allowance for Credit Losses, Recoveries	27	0	27	47
Provision/ (credit) for loan losses	(119)	192	20	(156)
Loans and Leases Receivable, Allowance at End of Period	9,804	10,282	9,804	10,282
Home equity [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and Leases Receivable, Allowance at Beginning of Period	784	987	835	1,035
Financing Receivable, Allowance for Credit Losses, Charge-offs	0	0	0	0
Financing Receivable, Allowance for Credit Losses, Recoveries	0	0	1	0
Provision/ (credit) for loan losses	552	(58)	500	(106)
Loans and Leases Receivable, Allowance at End of Period	1,336	929	1,336	929
Consumer and other [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and Leases Receivable, Allowance at Beginning of Period	126	302	630	391
Financing Receivable, Allowance for Credit Losses, Charge-offs	(15)	(245)	(39)	(245)
Financing Receivable, Allowance for Credit Losses, Recoveries	24	9	156	18
Provision/ (credit) for loan losses	12	339	(600)	241
Loans and Leases Receivable, Allowance at End of Period	$ 147	$ 405	$ 147	$ 405