Investments - Narrative (Details) - USD ($)	1 Months Ended	3 Months Ended	6 Months Ended
	Jan. 31, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Dec. 31, 2022
Debt Securities, Available-for-sale [Line Items]
Cumulative net unamortized unrealized gain			$ 195,000		$ 481,000
Maximum percentage of shareholders' equity security holdings held of one issuer			10.00%		10.00%
Securities pledged			$ 1,600,000,000		$ 734,500,000
Mortgage-backed securities, weighted average life			5 years
Provision for credit losses on available-for-sale securities			$ 5,000,000
Charge-off			5,000,000
Allowance for credit losses on available-for-sale securities			0		0
Accrued interest receivable, held-to-maturity securities			6,100,000		5,800,000
Allowance for credit losses on held-to-maturity securities			858,000		735,000
Sale of debt securities, available-for-sale	$ 28,400,000	$ 0	28,741,000	$ 0
Debt Securities, Available-for-sale, Realized Gain	$ 400,000
Other investments, at cost			66,487,000		63,790,000
Reclassified to Held to Maturity
Debt Securities, Available-for-sale [Line Items]
Cumulative net unamortized unrealized gain			15,900,000		17,600,000
Des Moines
Debt Securities, Available-for-sale [Line Items]
Other investments, at cost			$ 16,000,000		$ 14,000,000