Debt Securities - Narrative (Details)	12 Months Ended
	Dec. 31, 2020 USD ($) security	Dec. 31, 2019 USD ($)
Investments, Debt and Equity Securities [Abstract]
Debt securities pledged as collateral	$ 2,169,967,000	$ 1,475,752,000
Severity rate on available-for-sale debt securities in an unrealized loss position	5.00%
Number of credit rating categories, highest | security	4
Interest receivable, available-for-sale debt securities	$ 20,215,000
ACL on available-for-sale debt securities	0
Interest receivable, held-to-maturity debt securities	1,728,000
ACL on held-to-maturity debt securities	$ 0