Investments - Debt and Short-term Investments (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025	Dec. 31, 2025	Nov. 12, 2025
Investments
Other investments	$ 60,509		$ 59,281
Investment in unconsolidated investees	56,053		53,521
Cash	49,121		51,565
Short-term investments	386,219		120,562
Prime Holdings Insurance Services, Inc. (Prime)
Investments
Investment in unconsolidated investees	56,000		54,000
FHLBC
Investments
Investments pledged as collateral	$ 52,000
Investment in federal home loan bank stock	us-gaap:AssetPledgedAsCollateralMember
Amount borrowed from FHLB				$ 50,000
Federal home loan bank borrowings fair value disclosure	$ 50,000
Investment In Low Income Housing Tax Credit Partnerships (LIHTC)
Investments
Other investments	13,000		14,000
Total tax benefit on investments in tax credit partnership	1,000	$ 1,000
Qualified affordable housing project investments, unfunded commitment	8,000
Investment In Low Income Housing Tax Credit Partnerships (LIHTC) | Maximum
Investments
Amortization on tax credit partnership investments	$ 1,000	$ 1,000
Amortization of tax credit partnerships, Statement of Income	Income tax expense	Income tax expense
Historic tax credit partnerships (HTC)
Investments
Other investments	$ 10,000		11,000
Total tax benefit on investments in tax credit partnership	1,000	$ 1,000
Equity investments in tax credit structures, unfunded commitment	4,000
Historic tax credit partnerships (HTC) | Maximum
Investments
Amortization on tax credit partnership investments	$ 1,000	$ 1,000
Amortization of tax credit partnerships, Statement of Income	Income tax expense	Income tax expense
Investment in Private Funds
Investments
Other investments	$ 19,000		$ 18,000
Fair value investments entities that calculate net asset value per share, unfunded commitments	$ 2,000