Investments - Debt and Short-term Investments (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Dec. 31, 2024
Investments
Other investments	$ 60,357		$ 57,939
Investment in unconsolidated investees	56,684		56,477
Prime Holdings Insurance Services, Inc. (Prime)
Investments
Investment in unconsolidated investees	56,000
Other Unconsolidated Investees | Maximum
Investments
Investment in unconsolidated investees	1,000
FHLBC
Investments
Investments pledged as collateral	$ 56,000
Investment in federal home loan bank stock	us-gaap:AssetPledgedAsCollateralMember
Federal home loan bank borrowings fair value disclosure	$ 50,000
Investment In Low Income Housing Tax Credit Partnerships (LIHTC)
Investments
Other investments	11,000		7,000
Amortization on tax credit partnership investments	$ 1,000	$ 1,000
Amortization of tax credit partnerships, Statement of Income	Income tax expense	Income tax expense
Total tax benefit on investments in tax credit partnership	$ 1,000	$ 1,000
Qualified affordable housing project investments, unfunded commitment	5,000
Historic tax credit partnerships (HTC)
Investments
Other investments	14,000		15,000
Amortization on qualifying equity investments	$ 1,000	$ 1,000
Amortization of tax credit partnerships, Statement of Income	Income tax expense	Income tax expense
Total tax benefit on investments in tax credit partnership	$ 1,000	$ 1,000
Equity investments in tax credit structures, unfunded commitment	4,000
Investment in Private Funds
Investments
Other investments	21,000		$ 24,000
Fair value investments entities that calculate net asset value per share, unfunded commitments	$ 4,000