Loans, Allowance for Loan Losses and Credit Quality (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013		Dec. 31, 2012
Allowance for loans based on collective and individual evaluation of impairment by loan category
Ending Balance: Total Loans by Group	$ 4,556,029	[1]	$ 4,519,011	[1]
Ending Balance: Individually Evaluated for Impairment	72,967		66,659
Financing Receivable, Acquired with Deteriorated Credit Quality	27,332		32,054
Ending Balance: Collectively Evaluated for Impairment	4,455,730		4,420,298
Commercial and Industrial [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Ending Balance: Total Loans by Group	756,222		687,511
Ending Balance: Individually Evaluated for Impairment	9,646		8,575
Financing Receivable, Acquired with Deteriorated Credit Quality	0		0
Ending Balance: Collectively Evaluated for Impairment	746,576		678,936
Commercial Real Estate [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Ending Balance: Total Loans by Group	2,166,281		2,122,153
Ending Balance: Individually Evaluated for Impairment	39,805		33,868
Financing Receivable, Acquired with Deteriorated Credit Quality	18,114		21,853
Ending Balance: Collectively Evaluated for Impairment	2,108,362		2,066,432
Commercial Construction [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Ending Balance: Total Loans by Group	236,466		188,768
Ending Balance: Individually Evaluated for Impairment	100		0
Financing Receivable, Acquired with Deteriorated Credit Quality	0		0
Ending Balance: Collectively Evaluated for Impairment	236,366		188,768
Small Business [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Ending Balance: Total Loans by Group	75,273		78,594
Ending Balance: Individually Evaluated for Impairment	2,062		2,279
Financing Receivable, Acquired with Deteriorated Credit Quality	0		0
Ending Balance: Collectively Evaluated for Impairment	73,211		76,315
Residential Real Estate [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Ending Balance: Total Loans by Group	496,464		612,881
Ending Balance: Individually Evaluated for Impairment	15,786		15,373
Financing Receivable, Acquired with Deteriorated Credit Quality	8,888		9,821
Ending Balance: Collectively Evaluated for Impairment	471,790		587,687
Consumer Home Equity [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Ending Balance: Total Loans by Group	804,670		802,149
Ending Balance: Individually Evaluated for Impairment	4,131		4,435
Financing Receivable, Acquired with Deteriorated Credit Quality	330		380
Ending Balance: Collectively Evaluated for Impairment	800,209		797,334
Consumer Other [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Ending Balance: Total Loans by Group	20,653		26,955
Ending Balance: Individually Evaluated for Impairment	1,437		2,129
Financing Receivable, Acquired with Deteriorated Credit Quality	0		0
Ending Balance: Collectively Evaluated for Impairment	$ 19,216		$ 24,826

[1] The amount of deferred fees included in the ending balance was $2.4 million and $3.1 million at September 30, 2013 and December 31, 2012, respectively.