Allowance for Loan Losses - Allowance Rollforward (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan losses, beginning of period:	$ 81,238	$ 71,982
Provision/(credit) for loan losses	(7,004)	16,962
Loans charged -off:	(297)	(528)
Recoveries on loans previously charged-off:	73	180
Allowance for loan losses, end of period:	74,010	68,211
Adjustment
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan losses, beginning of period:		(20,385)
Adjusted Balance
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan losses, beginning of period:		51,597
Commercial and industrial
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan losses, beginning of period:	8,985	10,048
Provision/(credit) for loan losses	2,017	1,245
Loans charged -off:	(297)	(518)
Recoveries on loans previously charged-off:	39	45
Allowance for loan losses, end of period:	10,744	10,255
Commercial and industrial \| Adjustment
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan losses, beginning of period:		(565)
Paycheck Protection Program
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan losses, beginning of period:	159
Provision/(credit) for loan losses	20
Loans charged -off:	0
Recoveries on loans previously charged-off:	0
Allowance for loan losses, end of period:	179
Commercial tax-exempt
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan losses, beginning of period:	2,550	6,016
Provision/(credit) for loan losses	35	320
Loans charged -off:	0	0
Recoveries on loans previously charged-off:	0	0
Allowance for loan losses, end of period:	2,585	1,927
Commercial tax-exempt \| Adjustment
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan losses, beginning of period:		(4,409)
Commercial real estate
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan losses, beginning of period:	51,161	40,765
Provision/(credit) for loan losses	(5,404)	10,270
Loans charged -off:	0	0
Recoveries on loans previously charged-off:	0	0
Allowance for loan losses, end of period:	45,757	36,580
Commercial real estate \| Adjustment
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan losses, beginning of period:		(14,455)
Construction and land
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan losses, beginning of period:	4,041	5,119
Provision/(credit) for loan losses	(788)	2,748
Loans charged -off:	0	0
Recoveries on loans previously charged-off:	0	0
Allowance for loan losses, end of period:	3,253	5,709
Construction and land \| Adjustment
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan losses, beginning of period:		(2,158)
Residential
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan losses, beginning of period:	12,864	8,857
Provision/(credit) for loan losses	(2,689)	2,237
Loans charged -off:	0	0
Recoveries on loans previously charged-off:	3	0
Allowance for loan losses, end of period:	10,178	11,779
Residential \| Adjustment
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan losses, beginning of period:		685
Home equity
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan losses, beginning of period:	293	778
Provision/(credit) for loan losses	(64)	(72)
Loans charged -off:	0	0
Recoveries on loans previously charged-off:	0	132
Allowance for loan losses, end of period:	229	303
Home equity \| Adjustment
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan losses, beginning of period:		(535)
Consumer and other
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan losses, beginning of period:	1,185	399
Provision/(credit) for loan losses	(131)	214
Loans charged -off:	0	(10)
Recoveries on loans previously charged-off:	31	3
Allowance for loan losses, end of period:	$ 1,085	1,658
Consumer and other \| Adjustment
Allowance for Loan and Lease Losses [Roll Forward]
Allowance for loan losses, beginning of period:		$ 1,052

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

No definition available.

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- Definition

Amount of allowance for credit loss on financing receivable. Excludes allowance for financing receivable covered under loss sharing agreement.

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- Definition

Amount of increase in allowance for credit loss on financing receivable from recovery.

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- Definition

Amount of writeoff of financing receivable, charged against allowance for credit loss.

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- Definition

Amount of credit loss expense (reversal of expense) for financing receivable.

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