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CARES act maximum borrowing capacity under paycheck protection program loan.

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Pledged financial instruments not separately reported loans receivable pledged to secure undrawn line of credit.

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Processing fee payment threshold limit of loan amount.

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Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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Contractual interest rate for funds borrowed, under the debt agreement.

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Carrying amount as of the balance sheet date of interest earned but not received. Also called accrued interest or accrued interest receivable.

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Amount of deferred interest and fee income, unamortized costs incurred to originate loans and leases, unamortized loan commitments and loan syndication fees, and premiums over or discounts from face amounts of acquired loans. Excludes amounts for loans and leases covered under loss sharing agreements.

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Loans and Leases and the Allowance for Credit Losses - Additional Information (Details)	12 Months Ended
	Dec. 31, 2020 USD ($) Loan	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Loan and lease portfolio
Unamortized Loan Commitment and Origination Fees and Unamortized Discounts or Premiums	$ 4,100,000
Unearned income on loans and leases		$ 1,300,000
Commercial loans and residential mortgage loans pledged to secure an undrawn FRB line of credit	805,400,000	1,000,000,000.0
Residential mortgage loans pledged under a blanket pledge arrangement to secure FHLB advance	3,000,000,000.0	3,100,000,000
Net gains related to sales of residential mortgage loans	15,400,000	5,300,000	$ 1,500,000
Accrued Interest Receivable	$ 49,303,000	46,476,000
Number of paycheck protection loans \| Loan	4,435
Revolving loans, converted to term loan during the period	$ 2,900
Number of days non-accrual loans are not past due	30 days
Recorded Investment	$ 72,500,000	69,100,000
Available commitments to lend additional funds on loans modified as TDR	500,000	300,000
Consumer mortgage loans collateralized by residential real estate property that are in the process of foreclosure	$ 1,000,000.0
Consumer
Loan and lease portfolio
Number of loan and lease concessions - COVID-19 \| Loan	1,920
Loan and lease modifications, amount - COVID-19	$ 178,100,000
Commercial
Loan and lease portfolio
Number of loan and lease concessions - COVID-19 \| Loan	210
Loan and lease modifications, amount - COVID-19	$ 311,600,000
Classified
Loan and lease portfolio
Number of months up to which residential and home equity loans may be considered classified, even if they are current as to principal and interest	6 months
Classified \| Consumer
Loan and lease portfolio
Number of days past due for loans and leases in classified credit quality indicator	90 days
Accounting Standards Update 2016-13 \| Cumulative Effect, Period of Adoption, Adjustment
Loan and lease portfolio
Additional decrease in cumulative adjustment	$ 1,700,000
PPP Loans, Administered by the SBA
Loan and lease portfolio
Maximum borrowing capacity under paycheck protection program loan	$ 10,000,000
Loans interest rate	1.00%
Long-term debt, gross	$ 528,100,000
PPP Loan Processing Fees Threshold One
Loan and lease portfolio
Percentage of processing fees by SBA	5.00%
PPP Loan Processing Fees Threshold Two
Loan and lease portfolio
Percentage of processing fees by SBA	3.00%
PPP Loan Processing Fees Threshold Three
Loan and lease portfolio
Percentage of processing fees by SBA	1.00%
Accrued Interest Receivable
Loan and lease portfolio
Accrued Interest Receivable	$ 35,900,000	$ 30,700,000
Maximum \| PPP Loans, Administered by the SBA
Loan and lease portfolio
Loans maturity period	5 years
Maximum \| PPP Loan Processing Fees Threshold One
Loan and lease portfolio
Processing fee payment threshold limit of loan amount	$ 350,000
Maximum \| PPP Loan Processing Fees Threshold Two
Loan and lease portfolio
Processing fee payment threshold limit of loan amount	$ 2,000,000
Minimum [Member]
Loan and lease portfolio
Default period past due following modification of loans in TDR (in days)	60 days
Minimum [Member] \| PPP Loans, Administered by the SBA
Loan and lease portfolio
Loans maturity period	2 years
Minimum [Member] \| PPP Loan Processing Fees Threshold Two
Loan and lease portfolio
Processing fee payment threshold limit of loan amount	$ 350,000
Minimum [Member] \| PPP Loan Processing Fees Threshold Three
Loan and lease portfolio
Processing fee payment threshold limit of loan amount	2,000,000
Home Equity
Loan and lease portfolio
Residential mortgage loans pledged under a blanket pledge arrangement to secure FHLB advance	$ 596,000,000.0
Home Equity \| Classified
Loan and lease portfolio
Number of days past due for loans and leases in classified credit quality indicator	90 days
Maximum current loan-to-value ratio for residential mortgage and home equity loans to be considered as pass (as a percent)	60.00%
Residential Mortgage \| Classified
Loan and lease portfolio
Number of days past due for loans and leases in classified credit quality indicator	90 days
Maximum current loan-to-value ratio for residential mortgage and home equity loans to be considered as pass (as a percent)	60.00%
Residential Mortgage \| Maximum
Loan and lease portfolio
Period of time loan being fully amortized	40 years
Land Loan \| Maximum
Loan and lease portfolio
Period of time loan being fully amortized	360 months
Extending balloon payments	5 years