Loans, Allowance for Loan Losses and Credit Quality (Allowance Allocations) (Details) - USD ($) $ in Thousands		Mar. 31, 2019	Dec. 31, 2018
Allowance for loans based on collective and individual evaluation of impairment by loan category
Ending Balance: Collectively Evaluated for Impairment		$ 6,910,734	$ 6,838,339
Ending Balance: Individually Evaluated for Impairment		57,482	59,060
Financing Receivable, Net		4,944,644	4,874,718
Ending Balance: Total Loans by Group	[1]	6,976,872	6,906,194
Financial Asset Acquired with Credit Deterioration [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Financing Receivable, Net		8,656	8,795
Commercial and Industrial [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Ending Balance: Collectively Evaluated for Impairment		1,122,411	1,064,800
Ending Balance: Individually Evaluated for Impairment		28,221	28,829
Financing Receivable, Net		1,150,632	1,093,629
Ending Balance: Total Loans by Group	[1]	1,150,632	1,093,629
Commercial and Industrial [Member] | Financial Asset Acquired with Credit Deterioration [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		3,238,857	3,235,418
Ending Balance: Individually Evaluated for Impairment		10,323	10,839
Financing Receivable, Net		3,254,085	3,251,248
Ending Balance: Total Loans by Group	[1]	3,254,085	3,251,248
Commercial Real Estate [Member] | Financial Asset Acquired with Credit Deterioration [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Financing Receivable, Net		4,905	4,991
Construction Loans [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Ending Balance: Collectively Evaluated for Impairment		373,206	365,165
Ending Balance: Individually Evaluated for Impairment		311	0
Financing Receivable, Net		373,517	365,165
Ending Balance: Total Loans by Group	[1]	373,517	365,165
Construction Loans [Member] | Financial Asset Acquired with Credit Deterioration [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		165,931	164,135
Ending Balance: Individually Evaluated for Impairment		479	541
Financing Receivable, Net		166,410	164,676
Ending Balance: Total Loans by Group	[1]	166,410	164,676
Small Business [Member] | Financial Asset Acquired with Credit Deterioration [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		919,599	906,959
Ending Balance: Individually Evaluated for Impairment		12,061	12,706
Ending Balance: Total Loans by Group	[1]	935,238	923,294
Residential Real Estate [Member] | Financial Asset Acquired with Credit Deterioration [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Financing Receivable, Net		3,578	3,629
Consumer Home Equity [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Ending Balance: Collectively Evaluated for Impairment		1,074,668	1,085,961
Ending Balance: Individually Evaluated for Impairment		5,900	5,948
Ending Balance: Total Loans by Group	[1]	1,080,741	1,092,084
Consumer Home Equity [Member] | Financial Asset Acquired with Credit Deterioration [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Financing Receivable, Net		173	175
Consumer Other [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Ending Balance: Collectively Evaluated for Impairment		16,062	15,901
Ending Balance: Individually Evaluated for Impairment		187	197
Ending Balance: Total Loans by Group	[1],[2]	16,249	16,098
Consumer Other [Member] | Financial Asset Acquired with Credit Deterioration [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 $7.3 million and $7.1 million at March 31, 2019 and December 31, 2018, respectively. Net unamortized discounts on acquired loans not deemed to be purchased credit impaired ("PCI") included in the ending balance was $14.3 million and $15.2 million at March 31, 2019 and December 31, 2018, respectively.

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