Loans and Allowance for Credit Losses - Additional Information (Detail)	3 Months Ended
Mar. 31, 2020 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2019 USD ($)
Financing Receivable, Allowance for Credit Losses [Line Items]
Proceeds from sales of loans held for sale	$ 75,667,000	$ 21,258,000
Non- Accrual Loans	97,029,000		$ 56,347,000
Restructured loans	14,300,000		19,800,000
Total Past Due	118,664,000		79,910,000
Non accrual loans with no related allowance for credit losses	68,190,000
Accrued interest on loans	$ 44,100,000
Number of reasonable and supportable forecast period	1 year
Outstanding commitments to lend to borrowers with loan modifications classified as TDR's	$ 0	$ 0
Number of Contracts	0	0
Default payment of troubled restructuring, commercial real estate loan	$ 0	$ 0
Loan modifications not identified as TDR, due to effects of COVID-19	$ 7,000
Minimum [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Number of reasonable and supportable forecast period	1 year
Maximum [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Number of reasonable and supportable forecast period	3 years
Greater than 90 days Past Due and Accruing [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Total Past Due	$ 2,211,000		$ 2,069,000
Consumer Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Proceeds from sales of loans held for sale	$ 75,700,000	$ 21,300,000

Financing receivable modifications not identified as troubled debt restructuring.

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Number of financing receivables that have been modified by troubled debt restructurings.

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Amount of financing receivable on nonaccrual status with no allowance for credit loss.

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Amount of financing receivable past due.

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The cash inflow resulting from the sale of loans classified as held-for-sale, including proceeds from loans sold through mortgage securitization.

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