Allowance for Loan Losses Allowance Rollforward (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2016	Mar. 31, 2015
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and Leases Receivable, Allowance at Beginning of Period		$ 78,500	$ 75,838
Provision/ (credit) for loan losses		(3,133)	(2,500)
Financing Receivable, Allowance for Credit Losses, Charge-offs		(3,016)	(54)
Financing Receivable, Allowance for Credit Losses, Recoveries		4,076	3,979
Loans and Leases Receivable, Allowance at End of Period		76,427	77,263
Commercial and industrial [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and Leases Receivable, Allowance at Beginning of Period		15,814	14,114
Provision/ (credit) for loan losses		(657)	(1,981)
Financing Receivable, Allowance for Credit Losses, Charge-offs		(2,108)	0
Financing Receivable, Allowance for Credit Losses, Recoveries		1,294	2,204
Loans and Leases Receivable, Allowance at End of Period		14,343	14,337
Commercial real estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and Leases Receivable, Allowance at Beginning of Period		44,215	43,854
Provision/ (credit) for loan losses		(1,847)	(933)
Financing Receivable, Allowance for Credit Losses, Charge-offs		0	0
Financing Receivable, Allowance for Credit Losses, Recoveries		2,151	631
Loans and Leases Receivable, Allowance at End of Period		44,519	43,552
Construction and land [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and Leases Receivable, Allowance at Beginning of Period		6,322	4,041
Provision/ (credit) for loan losses		(998)	227
Financing Receivable, Allowance for Credit Losses, Charge-offs		(400)	0
Financing Receivable, Allowance for Credit Losses, Recoveries		627	1,143
Loans and Leases Receivable, Allowance at End of Period		5,551	5,411
Residential [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and Leases Receivable, Allowance at Beginning of Period		10,544	10,374
Provision/ (credit) for loan losses		591	72
Financing Receivable, Allowance for Credit Losses, Charge-offs		(501)	(49)
Financing Receivable, Allowance for Credit Losses, Recoveries		0	0
Loans and Leases Receivable, Allowance at End of Period		10,634	10,397
Home equity [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and Leases Receivable, Allowance at Beginning of Period		1,085	1,003
Provision/ (credit) for loan losses		(6)	13
Financing Receivable, Allowance for Credit Losses, Charge-offs		0	0
Financing Receivable, Allowance for Credit Losses, Recoveries		0	0
Loans and Leases Receivable, Allowance at End of Period		1,079	1,016
Consumer and other [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and Leases Receivable, Allowance at Beginning of Period		520	382
Provision/ (credit) for loan losses		(216)	130
Financing Receivable, Allowance for Credit Losses, Charge-offs		(7)	(5)
Financing Receivable, Allowance for Credit Losses, Recoveries		4	1
Loans and Leases Receivable, Allowance at End of Period		301	508
Unallocated Financing Receivables [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and Leases Receivable, Allowance at Beginning of Period	[1]	0	2,070
Provision/ (credit) for loan losses		0	(28)
Loans and Leases Receivable, Allowance at End of Period	[1]	$ 0	$ 2,042

[1] As of December 31, 2015, the unallocated reserve was allocated to the qualitative factors as part of the general reserves (ASC 450).