Loans, Allowance for Loan Losses and Credit Quality (Allowance Allocations) (Details) - USD ($) $ in Thousands		Sep. 30, 2019	Dec. 31, 2018
Allowance for loans based on collective and individual evaluation of impairment by loan category
Ending Balance: Collectively Evaluated for Impairment		$ 8,840,602	$ 6,838,339
Ending Balance: Individually Evaluated for Impairment		56,940	59,060
Financing Receivable, after Allowance for Credit Loss		6,104,626	4,874,718
Ending Balance: Total Loans by Group	[1]	8,913,501	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, after Allowance for Credit Loss		15,959	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		1,385,379	1,064,800
Ending Balance: Individually Evaluated for Impairment		26,137	28,829
Financing Receivable, after Allowance for Credit Loss		1,411,516	1,093,629
Ending Balance: Total Loans by Group	[1]	1,411,516	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, after Allowance for Credit Loss		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		3,979,670	3,235,418
Ending Balance: Individually Evaluated for Impairment		13,984	10,839
Financing Receivable, after Allowance for Credit Loss		4,000,487	3,251,248
Ending Balance: Total Loans by Group	[1]	4,000,487	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, after Allowance for Credit Loss		6,833	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		520,585	365,165
Ending Balance: Individually Evaluated for Impairment		0	0
Financing Receivable, after Allowance for Credit Loss		520,585	365,165
Ending Balance: Total Loans by Group	[1]	520,585	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, after Allowance for Credit Loss		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		171,723	164,135
Ending Balance: Individually Evaluated for Impairment		315	541
Financing Receivable, after Allowance for Credit Loss		172,038	164,676
Ending Balance: Total Loans by Group	[1]	172,038	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, after Allowance for Credit Loss		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		1,625,923	906,959
Ending Balance: Individually Evaluated for Impairment		11,039	12,706
Ending Balance: Total Loans by Group	[1]	1,644,758	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, after Allowance for Credit Loss		7,796	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		1,130,777	1,085,961
Ending Balance: Individually Evaluated for Impairment		5,325	5,948
Ending Balance: Total Loans by Group	[1]	1,137,109	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, after Allowance for Credit Loss		1,007	175
Consumer Other [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Ending Balance: Collectively Evaluated for Impairment		26,545	15,901
Ending Balance: Individually Evaluated for Impairment		140	197
Ending Balance: Total Loans by Group	[1],[2]	27,008	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, after Allowance for Credit Loss		$ 323	$ 0

[1] The amount of net deferred costs on originated loans included in the ending balance was $7.2 million and $7.1 million at September 30, 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 $24.7 million and $15.2 million at September 30, 2019 and December 31, 2018, respectively.

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