Allowance for Loan Losses Allowance Rollforward (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and Leases Receivable, Allowance at Beginning of Period	$ 75,009	$ 75,753	$ 78,077	$ 78,500
Financing Receivable, Allowance for Credit Losses, Charge-offs	(38)	(337)	(559)	(3,372)
Financing Receivable, Allowance for Credit Losses, Recoveries	334	2,391	4,082	8,347
Provision/ (credit) for loan losses	(432)	(138)	(6,727)	(5,806)
Loans and Leases Receivable, Allowance at End of Period	74,873	77,669	74,873	77,669
Commercial and Industrial Portfolio Segment [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and Leases Receivable, Allowance at Beginning of Period	11,672	13,246	12,751	15,814
Financing Receivable, Allowance for Credit Losses, Charge-offs	0	(285)	(218)	(2,393)
Financing Receivable, Allowance for Credit Losses, Recoveries	241	81	395	1,457
Provision/ (credit) for loan losses	973	859	(42)	(977)
Loans and Leases Receivable, Allowance at End of Period	12,886	13,901	12,886	13,901
Commercial real estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and Leases Receivable, Allowance at Beginning of Period	48,136	45,507	50,412	44,215
Financing Receivable, Allowance for Credit Losses, Charge-offs	0	0	0	0
Financing Receivable, Allowance for Credit Losses, Recoveries	76	1,767	3,605	5,709
Provision/ (credit) for loan losses	(1,173)	1,038	(6,978)	(1,612)
Loans and Leases Receivable, Allowance at End of Period	47,039	48,312	47,039	48,312
Construction and land [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and Leases Receivable, Allowance at Beginning of Period	3,585	4,740	3,039	6,322
Financing Receivable, Allowance for Credit Losses, Charge-offs	0	0	0	(400)
Financing Receivable, Allowance for Credit Losses, Recoveries	13	490	13	1,117
Provision/ (credit) for loan losses	182	(2,086)	728	(3,895)
Loans and Leases Receivable, Allowance at End of Period	3,780	3,144	3,780	3,144
Residential [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and Leases Receivable, Allowance at Beginning of Period	10,282	10,752	10,449	10,544
Financing Receivable, Allowance for Credit Losses, Charge-offs	0	0	(58)	(501)
Financing Receivable, Allowance for Credit Losses, Recoveries	0	49	47	53
Provision/ (credit) for loan losses	(431)	103	(587)	808
Loans and Leases Receivable, Allowance at End of Period	9,851	10,904	9,851	10,904
Home equity [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and Leases Receivable, Allowance at Beginning of Period	929	1,139	1,035	1,085
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	(15)	(62)	(121)	(8)
Loans and Leases Receivable, Allowance at End of Period	914	1,077	914	1,077
Consumer and other [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and Leases Receivable, Allowance at Beginning of Period	405	369	391	520
Financing Receivable, Allowance for Credit Losses, Charge-offs	(38)	(52)	(283)	(78)
Financing Receivable, Allowance for Credit Losses, Recoveries	4	4	22	11
Provision/ (credit) for loan losses	32	10	273	(122)
Loans and Leases Receivable, Allowance at End of Period	$ 403	$ 331	$ 403	$ 331