Investments - Debt and Short-term Investments (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
Investments
Other investments	$ 55,364		$ 55,364		$ 59,081
Investment in unconsolidated investees	67,249		67,249		56,966
Cash and Short-term Investments
Cash	50,030		50,030		36,424
Short-term investments	125,865		125,865		134,923
Other Unconsolidated Investees | Maximum
Investments
Investment in unconsolidated investees	1,000		1,000
Prime Holdings Insurance Services, Inc. (Prime)
Investments
Investment in unconsolidated investees	67,000		67,000
FHLBC
Investments
Investments pledged as collateral	$ 57,000		$ 57,000
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	9,000		9,000		10,000
Amortization on low income housing investments	$ 1,000	$ 1,000	$ 1,000	$ 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	$ 1,000	$ 2,000
Investment In Low Income Housing Tax Credit Partnerships (LIHTC) | Maximum
Investments
Qualified affordable housing project investments, unfunded commitment	1,000		1,000
Historic tax credit partnerships (HTC)
Investments
Other investments	11,000		11,000		13,000
Amortization on qualifying equity 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	$ 3,000	$ 3,000
Investment in Private Funds
Investments
Other investments	25,000		25,000		$ 28,000
Fair value investments entities that calculate net asset value per share, unfunded commitments	$ 4,000		$ 4,000