Allowance for Credit Losses - Additional Information (Details) - USD ($)	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020	Dec. 31, 2019	Mar. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses attributable to restructured loans	$ 173,106,000	$ 120,185,000	$ 176,144,000	$ 52,162,000
Provision for loan losses	$ 0	26,350,000
Supportable period	2 years
Interest receivable	$ 56,199,000		56,459,000
Deferred interest, allowance for credit loss	1,375,000		1,500,000
Cumulative Effect, Period Of Adoption, Adjustment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses attributable to restructured loans			42,484,000
Real estate – construction:
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses attributable to restructured loans	14,977,000	10,924,000	16,047,000	$ 5,029,000
Provision for loan losses	(1,031,000)	2,390,000
Real estate – construction: | Cumulative Effect, Period Of Adoption, Adjustment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses attributable to restructured loans			3,505,000
Lease financing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses attributable to restructured loans	1,546,000	1,588,000	1,624,000		$ 910,000
Provision for loan losses	$ (89,000)	$ 152,000
Lease financing | Cumulative Effect, Period Of Adoption, Adjustment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan losses attributable to restructured loans			$ 521,000