Loans, Allowance for Loan Losses and Credit Quality (Details) (USD $) In Thousands, unless otherwise specified	Jun. 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	$ 4,530,111	[1]	$ 4,519,011	[1]
Ending Balance: Individually Evaluated for Impairment	71,381		66,659
Financing Receivable, Acquired with Deteriorated Credit Quality	27,675		32,054
Ending Balance: Collectively Evaluated for Impairment	4,431,055		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	742,343		687,511
Ending Balance: Individually Evaluated for Impairment	9,759		8,575
Financing Receivable, Acquired with Deteriorated Credit Quality	0		0
Ending Balance: Collectively Evaluated for Impairment	732,584		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	2,150,833		2,122,153
Ending Balance: Individually Evaluated for Impairment	36,439		33,868
Financing Receivable, Acquired with Deteriorated Credit Quality	18,304		21,853
Ending Balance: Collectively Evaluated for Impairment	2,096,090		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	231,719		188,768
Ending Balance: Individually Evaluated for Impairment	1,608		0
Financing Receivable, Acquired with Deteriorated Credit Quality	0		0
Ending Balance: Collectively Evaluated for Impairment	230,111		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	77,283		78,594
Ending Balance: Individually Evaluated for Impairment	2,039		2,279
Financing Receivable, Acquired with Deteriorated Credit Quality	0		0
Ending Balance: Collectively Evaluated for Impairment	75,244		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	513,551		612,881
Ending Balance: Individually Evaluated for Impairment	15,883		15,373
Financing Receivable, Acquired with Deteriorated Credit Quality	8,991		9,821
Ending Balance: Collectively Evaluated for Impairment	488,677		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	792,450		802,149
Ending Balance: Individually Evaluated for Impairment	4,069		4,435
Financing Receivable, Acquired with Deteriorated Credit Quality	380		380
Ending Balance: Collectively Evaluated for Impairment	788,001		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	21,932		26,955
Ending Balance: Individually Evaluated for Impairment	1,584		2,129
Financing Receivable, Acquired with Deteriorated Credit Quality	0		0
Ending Balance: Collectively Evaluated for Impairment	$ 20,348		$ 24,826

[1] The amount of deferred fees included in the ending balance was $2.6 million and $3.1 million at June 30, 2013 and December 31, 2012, respectively.