Investments - Narrative (Details)	12 Months Ended
	Dec. 31, 2023 USD ($) number_of_securities	Dec. 31, 2022 USD ($) number_of_securities	Dec. 31, 2021 USD ($)
Debt Securities, Available-for-sale [Line Items]
Amortized cost	$ 1,769,134,000	$ 1,729,054,000
Other investments	$ 66,195,000	$ 63,790,000
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions | number_of_securities	753	740
Gross Unrealized Gains	$ 1,603,000	$ 481,000
Maximum percentage of shareholders' equity security holdings held of one issuer	10.00%	10.00%
Available-for-sale securities pledged as collateral, fair value	$ 1,600,000,000	$ 734,500,000
Weighted average life (in years)	5 years
ACL on held-to-maturity securities	$ 785,000	735,000
Sale of debt securities, available-for-sale	40,393,000	0	$ 27,135,000
Gross gains realized	601,000	0	$ 0
Provisions For Credit Losses, Available-For-Sale	4,200,000
Debt Securities, Provision For Credit Losses, Chargeoff	4,200,000
Debt Securities, Available-for-Sale, Allowance for Credit Loss, Excluding Accrued Interest	0	0
Accrued interest receivable, held-to-maturity securities	6,500,000	5,800,000
Des Moines
Debt Securities, Available-for-sale [Line Items]
Other investments	7,800,000	14,000,000
Reclassified to Held to Maturity [Member]
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Gains	14,100,000	17,600,000
Debt Securities, Available-for-sale, Amortized Cost	$ 0	$ 116,700,000