Loans, Allowance for Loan Losses and Credit Quality (Allowance Allocations) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		12 Months Ended
	Sep. 30, 2014		Dec. 31, 2013
Financing Receivable, Allowance for Credit Losses [Line Items]
Amortization of Deferred Loan Origination Fees, Net	$ 2,726		$ 2,346
Allowance for loans based on collective and individual evaluation of impairment by loan category
Ending Balance: Total Loans by Group	4,947,855	[1]	4,718,307	[1]
Ending Balance: Individually Evaluated for Impairment	64,881		72,055
Financing Receivable, Acquired with Deteriorated Credit Quality	25,285		29,544
Ending Balance: Collectively Evaluated for Impairment	4,857,689		4,616,708
Commercial and Industrial [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Ending Balance: Total Loans by Group	842,833		784,202
Ending Balance: Individually Evaluated for Impairment	7,592		9,148
Financing Receivable, Acquired with Deteriorated Credit Quality	0		1
Ending Balance: Collectively Evaluated for Impairment	835,241		775,053
Commercial Real Estate [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Ending Balance: Total Loans by Group	2,338,641		2,249,260
Ending Balance: Individually Evaluated for Impairment	33,765		39,516
Financing Receivable, Acquired with Deteriorated Credit Quality	15,071		18,612
Ending Balance: Collectively Evaluated for Impairment	2,289,805		2,191,132
Commercial Construction [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Ending Balance: Total Loans by Group	276,593		223,859
Ending Balance: Individually Evaluated for Impairment	311		100
Financing Receivable, Acquired with Deteriorated Credit Quality	184		197
Ending Balance: Collectively Evaluated for Impairment	276,098		223,562
Small Business [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Ending Balance: Total Loans by Group	81,435		77,240
Ending Balance: Individually Evaluated for Impairment	1,244		1,903
Financing Receivable, Acquired with Deteriorated Credit Quality	0		0
Ending Balance: Collectively Evaluated for Impairment	80,191		75,337
Residential Real Estate [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Ending Balance: Total Loans by Group	536,822		541,443
Ending Balance: Individually Evaluated for Impairment	15,503		15,200
Financing Receivable, Acquired with Deteriorated Credit Quality	9,784		10,389
Ending Balance: Collectively Evaluated for Impairment	511,535		515,854
Consumer Home Equity [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Ending Balance: Total Loans by Group	854,646		822,141
Ending Balance: Individually Evaluated for Impairment	5,492		4,890
Financing Receivable, Acquired with Deteriorated Credit Quality	241		326
Ending Balance: Collectively Evaluated for Impairment	848,913		816,925
Consumer Other [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Ending Balance: Total Loans by Group	16,885		20,162
Ending Balance: Individually Evaluated for Impairment	974		1,298
Financing Receivable, Acquired with Deteriorated Credit Quality	5		19
Ending Balance: Collectively Evaluated for Impairment	$ 15,906		$ 18,845

[1] The amount of net deferred fees included in the ending balance was $2.7 million and $2.3 million at September 30, 2014 and December 31, 2013.