Loans, Allowance for Credit Losses and Credit Quality Textual (Details)		3 Months Ended				9 Months Ended
		Sep. 30, 2021 USD ($)		Sep. 30, 2020 USD ($)		Sep. 30, 2021 USD ($) loan		Sep. 30, 2020 USD ($)		Dec. 31, 2020 USD ($)
Financing Receivable, Allowance for Credit Loss [Line Items]
Days To Be Termed As Non Accrual Loans						90 days
Financing Receivable, Allowance for Credit Loss, Period Increase (Decrease) by percentage		(9.90%)
Provision for credit losses		$ (10,000,000)		$ 7,500,000		$ (17,500,000)		$ 52,500,000
Interest Receivable		29,100,000		36,700,000		29,100,000		36,700,000
Off-Balance Sheet, Credit Loss, Liability		1,300,000				1,300,000				$ 1,200,000
Loans with active Deferrals		222,900,000				222,900,000				173,600,000
Allowance for Loan and Lease Losses, Write-offs		(332,000)
Financing Receivable, Troubled Debt Restructuring, Increase (Decrease) from Modification								3,639,000
us-gaap_FinancingReceivableTroubledDebtRestructuringIncreaseDecreaseFromModification		14,300,000		83,000				1,500,000
Financing Receivable, after Allowance for Credit Loss		1,845,455,000		2,199,885,000		1,845,455,000		2,199,885,000
Financing Receivable, Troubled Debt Restructuring, Subsequent Default				0		$ 3,200,000		0
Financing Receivable, Troubled Debt Restructuring, Subsequent Default, Number of Contracts | loan						1
Loans with active Deferrals		222,900,000				$ 222,900,000				173,600,000
Financing Receivable, Allowance for Credit Losses, Effect of Change in Method	[1]							(1,137,000)
Interest Receivable		29,100,000		36,700,000		29,100,000		36,700,000
Loans and Leases Receivable, Allowance		(92,246,000)	[2]	(115,625,000)	[2]	(92,246,000)	[2]	(115,625,000)	[2]	(113,392,000)
Off-Balance Sheet, Credit Loss, Liability		1,300,000				1,300,000				1,200,000
Accounts Receivable, Allowance for Credit Loss, Period Increase (Decrease)		10,100,000
Financing Receivable, Troubled Debt Restructuring, Subsequent Default				0		3,200,000		0
US Government Insured Loan Program [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss		367,300,000		811,700,000		367,300,000		811,700,000		16,300,000
Commercial And Industrial [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Provision for credit losses				2,741,000		(1,698,000)		12,698,000
Financing Receivable, before Allowance for Credit Loss		1,640,709,000				1,640,709,000				$ 2,103,152,000
Allowance for Loan and Lease Losses, Write-offs		(1,000)
Financing Receivable, after Allowance for Credit Loss		608,467,000		1,018,266,000		608,467,000		1,018,266,000
Financing Receivable, Allowance for Credit Losses, Effect of Change in Method	[1]							(1,984,000)
Loans and Leases Receivable, Allowance	[2]	(16,014,000)		(28,219,000)		(16,014,000)		(28,219,000)
Commercial And Industrial [Member] | Definite Weakness Loss Unlikely [Member]
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, after Allowance for Credit Loss		16,597,000		$ 2,732,000		16,597,000		$ 2,732,000
Loans Insured or Guaranteed by US Government Authorities
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, before Allowance for Credit Loss		$ 383,600,000				$ 383,600,000

[1] Represents adjustment needed to reflect the cumulative day one impact pursuant to the Company's adoption of Accounting Standards Update 2016-13. The adjustment represents a $1.1 million decrease to the allowance attributable to the change in accounting methodology for estimating the allowance for credit losses resulting from the Company's adoption of the standard.

[2] Balances of accrued interest receivable excluded from amortized cost and the calculation of allowance for credit losses amounted to $29.1 million and $36.7 million as of September 30, 2021 and September 30, 2020, respectively.