Investments - Debt and Short-term Investments (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024	Dec. 31, 2024
Investments
Other investments	$ 56,494		$ 56,494		$ 57,939
Investment in unconsolidated investees	63,652		63,652		56,477
Cash	52,621		52,621		39,790
Short-term investments	165,706		165,706		74,915
Prime Holdings Insurance Services, Inc. (Prime)
Investments
Investment in unconsolidated investees	63,000		63,000
Other Unconsolidated Investees | Maximum
Investments
Investment in unconsolidated investees	1,000		1,000
FHLBC
Investments
Investments pledged as collateral	$ 55,000		$ 55,000
Investment in federal home loan bank stock	us-gaap:AssetPledgedAsCollateralMember		us-gaap:AssetPledgedAsCollateralMember
Federal home loan bank borrowings fair value disclosure	$ 50,000		$ 50,000
Investment In Low Income Housing Tax Credit Partnerships (LIHTC)
Investments
Other investments	10,000		10,000		7,000
Amortization on tax credit partnership investments	$ 1,000	$ 1,000	$ 2,000	$ 2,000
Amortization of tax credit partnerships, Statement of Income	Income tax expense	Income tax expense	Income tax expense	Income tax expense
Total tax benefit on investments in tax credit partnership	$ 1,000	$ 1,000	$ 2,000	$ 2,000
Qualified affordable housing project investments, unfunded commitment	4,000		4,000
Historic tax credit partnerships (HTC)
Investments
Other investments	12,000		12,000		15,000
Amortization on tax credit partnership investments	$ 1,000	$ 1,000	$ 3,000	$ 3,000
Amortization of tax credit partnerships, Statement of Income	Income tax expense	Income tax expense	Income tax expense	Income tax expense
Total tax benefit on investments in tax credit partnership	$ 1,000	$ 2,000	$ 3,000	$ 4,000
Equity investments in tax credit structures, unfunded commitment	4,000		4,000
Investment in Private Funds
Investments
Other investments	18,000		18,000		$ 24,000
Fair value investments entities that calculate net asset value per share, unfunded commitments	$ 3,000		$ 3,000