Loans, Allowance for Loan Losses and Credit Quality (ALLL - by category) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Financing Receivable Impaired [Line Items]
Financing Receivable, Collectively Evaluated for Impairment					$ 8,809,155
Financing Receivable, Individually Evaluated for Impairment					49,628
Financing Receivable, after Allowance for Credit Loss					6,119,185
Summary of changes in allowance for loan losses
Beginning Balance		$ 65,140	$ 67,740	$ 64,293
Charge-offs		472		(1,031)
Recoveries		292		698
Provision for credit losses	$ 20,000	1,000	45,000	2,000
Ending Balance	112,176	65,960	112,176	65,960
Ending Balance: Individually Evaluated for Impairment	1,073		1,073		980
Ending Balance: Collectively Evaluated for Impairment	64,887		64,887
Loans and Leases Receivable, Gross	9,359,648		9,359,648		8,873,639
Commercial and Industrial [Member]
Financing Receivable Impaired [Line Items]
Financing Receivable, Collectively Evaluated for Impairment					1,370,580
Financing Receivable, Individually Evaluated for Impairment					24,456
Financing Receivable, after Allowance for Credit Loss					1,395,036
Summary of changes in allowance for loan losses
Beginning Balance		16,872		15,760
Charge-offs		0		0
Recoveries		0		124
Provision for credit losses		(15)		973
Ending Balance	16,857		16,857
Ending Balance: Individually Evaluated for Impairment	7		7		126
Ending Balance: Collectively Evaluated for Impairment	16,850		16,850
Financing Receivable, before Allowance for Credit Loss	2,004,645		2,004,645		1,395,036
Loans and Leases Receivable, Gross	2,004,645		2,004,645		1,395,036
Commercial Real Estate [Member]
Financing Receivable Impaired [Line Items]
Financing Receivable, Collectively Evaluated for Impairment					3,987,848
Financing Receivable, Individually Evaluated for Impairment					8,337
Financing Receivable, after Allowance for Credit Loss					4,002,359
Summary of changes in allowance for loan losses
Beginning Balance		32,049		32,370
Charge-offs		0		0
Recoveries		13		46
Provision for credit losses		598		244
Ending Balance	32,660		32,660
Ending Balance: Individually Evaluated for Impairment	74		74		48
Ending Balance: Collectively Evaluated for Impairment	32,586		32,586
Financing Receivable, before Allowance for Credit Loss	4,071,047		4,071,047		4,002,359
Loans and Leases Receivable, Gross	4,071,047		4,071,047		4,002,359
Construction Loans [Member]
Financing Receivable Impaired [Line Items]
Financing Receivable, Collectively Evaluated for Impairment					547,293
Financing Receivable, Individually Evaluated for Impairment					0
Financing Receivable, after Allowance for Credit Loss					547,293
Summary of changes in allowance for loan losses
Beginning Balance		5,355		5,158
Charge-offs		0		0
Recoveries		0		0
Provision for credit losses		238		435
Ending Balance	5,593		5,593
Ending Balance: Individually Evaluated for Impairment	0		0
Ending Balance: Collectively Evaluated for Impairment	5,593		5,593
Financing Receivable, before Allowance for Credit Loss	537,788		537,788		547,293
Loans and Leases Receivable, Gross	537,788		537,788		547,293
Small Business [Member]
Financing Receivable Impaired [Line Items]
Financing Receivable, Collectively Evaluated for Impairment					173,960
Financing Receivable, Individually Evaluated for Impairment					537
Financing Receivable, after Allowance for Credit Loss					174,497
Summary of changes in allowance for loan losses
Beginning Balance		1,784		1,756
Charge-offs		49		(194)
Recoveries		20		47
Provision for credit losses		13		159
Ending Balance	1,768		1,768
Ending Balance: Individually Evaluated for Impairment	38		38		8
Ending Balance: Collectively Evaluated for Impairment	1,730		1,730
Financing Receivable, before Allowance for Credit Loss	170,288		170,288		174,497
Loans and Leases Receivable, Gross	170,288		170,288		174,497
Residential Real Estate [Member]
Financing Receivable Impaired [Line Items]
Financing Receivable, Collectively Evaluated for Impairment					1,571,848
Financing Receivable, Individually Evaluated for Impairment					11,228
Summary of changes in allowance for loan losses
Beginning Balance		3,234		3,219
Charge-offs		0		0
Recoveries		0		1
Provision for credit losses		62		76
Ending Balance	3,296		3,296
Ending Balance: Individually Evaluated for Impairment	789		789		637
Ending Balance: Collectively Evaluated for Impairment	2,507		2,507
Financing Receivable, before Allowance for Credit Loss	1,431,129		1,431,129		1,590,569
Loans and Leases Receivable, Gross	1,431,129		1,431,129		1,590,569
Consumer Home Equity [Member]
Financing Receivable Impaired [Line Items]
Financing Receivable, Collectively Evaluated for Impairment					1,127,963
Financing Receivable, Individually Evaluated for Impairment					4,948
Summary of changes in allowance for loan losses
Beginning Balance		5,507		5,608
Charge-offs		71		(184)
Recoveries		18		84
Provision for credit losses		93		39
Ending Balance	5,547		5,547
Ending Balance: Individually Evaluated for Impairment	159		159		156
Ending Balance: Collectively Evaluated for Impairment	5,388		5,388
Loans and Leases Receivable, Gross	1,120,523		1,120,523		1,133,798
Consumer - Other [Member]
Financing Receivable Impaired [Line Items]
Financing Receivable, Collectively Evaluated for Impairment					29,663
Financing Receivable, Individually Evaluated for Impairment					122
Summary of changes in allowance for loan losses
Beginning Balance		339		422
Charge-offs		352		(653)
Recoveries		241		396
Provision for credit losses		$ 11		$ 74
Ending Balance	239		239
Ending Balance: Individually Evaluated for Impairment	6		6		5
Ending Balance: Collectively Evaluated for Impairment	233		233
Financing Receivable, before Allowance for Credit Loss	24,228		24,228		30,087
Loans and Leases Receivable, Gross	$ 24,228		$ 24,228		30,087	[1]
Financial Asset Acquired with Credit Deterioration [Member]
Financing Receivable Impaired [Line Items]
Financing Receivable, after Allowance for Credit Loss					14,856
Financial Asset Acquired with Credit Deterioration [Member] | Commercial and Industrial [Member]
Financing Receivable Impaired [Line Items]
Financing Receivable, after Allowance for Credit Loss					0
Financial Asset Acquired with Credit Deterioration [Member] | Commercial Real Estate [Member]
Financing Receivable Impaired [Line Items]
Financing Receivable, after Allowance for Credit Loss					6,174
Financial Asset Acquired with Credit Deterioration [Member] | Construction Loans [Member]
Financing Receivable Impaired [Line Items]
Financing Receivable, after Allowance for Credit Loss					0
Financial Asset Acquired with Credit Deterioration [Member] | Small Business [Member]
Financing Receivable Impaired [Line Items]
Financing Receivable, after Allowance for Credit Loss					0
Financial Asset Acquired with Credit Deterioration [Member] | Residential Real Estate [Member]
Financing Receivable Impaired [Line Items]
Financing Receivable, after Allowance for Credit Loss					7,493
Financial Asset Acquired with Credit Deterioration [Member] | Consumer Home Equity [Member]
Financing Receivable Impaired [Line Items]
Financing Receivable, after Allowance for Credit Loss					887
Financial Asset Acquired with Credit Deterioration [Member] | Consumer - Other [Member]
Financing Receivable Impaired [Line Items]
Financing Receivable, after Allowance for Credit Loss					$ 302

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