Securities - Additional Information (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Financing Receivable, Nonaccrual [Line Items]
Available-for-sale securities pledged	$ 2,100,000,000		$ 2,100,000,000		$ 1,600,000,000
Held-to-maturity securities pledged as collateral	0		0		0
Realized gains (losses) on securities available-for-sale	0	$ 14,328,000	0	$ 13,323,000
Securities Receivable
Financing Receivable, Nonaccrual [Line Items]
Accrued interest receivable	$ 10,400,000		$ 10,400,000		$ 11,900,000