Loans, Allowance for Loan Losses and Credit Quality (Allowance Allocations) (Details) - USD ($) $ in Thousands		Jun. 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		$ 8,880,512	$ 6,838,339
Ending Balance: Individually Evaluated for Impairment		54,163	59,060
Financing Receivable, after Allowance for Credit Loss		6,124,515	4,874,718
Ending Balance: Total Loans by Group	[1]	8,950,787	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		16,112	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		1,373,573	1,064,800
Ending Balance: Individually Evaluated for Impairment		27,351	28,829
Financing Receivable, after Allowance for Credit Loss		1,400,924	1,093,629
Ending Balance: Total Loans by Group	[1]	1,400,924	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		4,042,092	3,235,418
Ending Balance: Individually Evaluated for Impairment		9,069	10,839
Financing Receivable, after Allowance for Credit Loss		4,058,066	3,251,248
Ending Balance: Total Loans by Group	[1]	4,058,066	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		6,905	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		491,598	365,165
Ending Balance: Individually Evaluated for Impairment		0	0
Financing Receivable, after Allowance for Credit Loss		491,598	365,165
Ending Balance: Total Loans by Group	[1]	491,598	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		173,397	164,135
Ending Balance: Individually Evaluated for Impairment		530	541
Financing Receivable, after Allowance for Credit Loss		173,927	164,676
Ending Balance: Total Loans by Group	[1]	173,927	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		1,636,033	906,959
Ending Balance: Individually Evaluated for Impairment		11,351	12,706
Ending Balance: Total Loans by Group	[1]	1,655,182	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		7,798	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		1,137,736	1,085,961
Ending Balance: Individually Evaluated for Impairment		5,689	5,948
Ending Balance: Total Loans by Group	[1]	1,144,499	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		1,074	175
Consumer Other [Member]
Allowance for loans based on collective and individual evaluation of impairment by loan category
Ending Balance: Collectively Evaluated for Impairment		26,083	15,901
Ending Balance: Individually Evaluated for Impairment		173	197
Ending Balance: Total Loans by Group	[1],[2]	26,591	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		$ 335	$ 0

[1] The amount of net deferred costs on originated loans included in the ending balance was $7.9 million and $7.1 million at June 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 $29.8 million and $15.2 million at June 30, 2019 and December 31, 2018, respectively.

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