Loans, Allowance for Loan Losses and Credit Quality (Allowance Allocations) (Details) - USD ($) $ in Thousands		Jun. 30, 2018	Dec. 31, 2017
Allowance for loans based on collective and individual evaluation of impairment by loan category
Ending Balance: Collectively Evaluated for Impairment		$ 6,399,926	$ 6,269,729
Ending Balance: Individually Evaluated for Impairment		68,080	72,801
Financing Receivable, Net		4,618,963	4,539,256
Ending Balance: Total Loans by Group	[1]	6,479,271	6,355,553
Receivables Acquired with Deteriorated Credit Quality [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Financing Receivable, Net		11,265	13,023
Commercial and Industrial [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Ending Balance: Collectively Evaluated for Impairment		943,722	853,885
Ending Balance: Individually Evaluated for Impairment		32,542	34,643
Financing Receivable, Net		976,264	888,528
Ending Balance: Total Loans by Group	[1]	976,264	888,528
Commercial and Industrial [Member] | Receivables Acquired with Deteriorated Credit Quality [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Financing Receivable, Net		0	0
Commercial Real Estate [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Ending Balance: Collectively Evaluated for Impairment		3,110,500	3,093,945
Ending Balance: Individually Evaluated for Impairment		15,016	16,638
Financing Receivable, Net		3,131,337	3,116,561
Ending Balance: Total Loans by Group	[1]	3,131,337	3,116,561
Commercial Real Estate [Member] | Receivables Acquired with Deteriorated Credit Quality [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Financing Receivable, Net		5,821	5,978
Construction Loans [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Ending Balance: Collectively Evaluated for Impairment		364,225	401,797
Ending Balance: Individually Evaluated for Impairment		0	0
Financing Receivable, Net		364,225	401,797
Ending Balance: Total Loans by Group	[1]	364,225	401,797
Construction Loans [Member] | Receivables Acquired with Deteriorated Credit Quality [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Financing Receivable, Net		0	0
Small Business [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Ending Balance: Collectively Evaluated for Impairment		146,334	131,667
Ending Balance: Individually Evaluated for Impairment		803	703
Financing Receivable, Net		147,137	132,370
Ending Balance: Total Loans by Group	[1]	147,137	132,370
Small Business [Member] | Receivables Acquired with Deteriorated Credit Quality [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Financing Receivable, Net		0	0
Residential Real Estate [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Ending Balance: Collectively Evaluated for Impairment		761,476	733,809
Ending Balance: Individually Evaluated for Impairment		12,705	13,684
Ending Balance: Total Loans by Group	[1]	779,421	754,329
Residential Real Estate [Member] | Receivables Acquired with Deteriorated Credit Quality [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Financing Receivable, Net		5,240	6,836
Consumer Home Equity [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Ending Balance: Collectively Evaluated for Impairment		1,062,334	1,045,053
Ending Balance: Individually Evaluated for Impairment		6,759	6,826
Ending Balance: Total Loans by Group	[1]	1,069,297	1,052,088
Consumer Home Equity [Member] | Receivables Acquired with Deteriorated Credit Quality [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Financing Receivable, Net		204	209
Consumer Other [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Ending Balance: Collectively Evaluated for Impairment		11,335	9,573
Ending Balance: Individually Evaluated for Impairment		255	307
Ending Balance: Total Loans by Group	[1]	11,590	9,880	[2]
Consumer Other [Member] | Receivables Acquired with Deteriorated Credit Quality [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Financing Receivable, Net		$ 0	$ 0

[1] The amount of net deferred costs on originated loans included in the ending balance was $6.7 million and $6.1 million at June 30, 2018 and December 31, 2017, respectively. Net unamortized discounts on acquired loans not deemed to be purchased credit impaired ("PCI") included in the ending balance was $8.8 million and $9.4 million at June 30, 2018 and December 31, 2017, respectively.

[2] (1) Other consumer portfolio is inclusive of deposit account overdrafts recorded as loan balances.