Investments - Debt and Short-term Investments (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Dec. 31, 2022
Investment Holdings [Line Items]
Other investments	$ 60,907		$ 60,907		$ 47,922
Investment in federal home loan bank stock	us-gaap:AssetPledgedAsCollateralMember		us-gaap:AssetPledgedAsCollateralMember		us-gaap:AssetPledgedAsCollateralMember
Cash and Short-term Investments
Investment in unconsolidated investees	$ 55,250		$ 55,250		$ 58,275
Cash	16,707		16,707		22,818
Short-term investments	271,296		271,296		36,229
Prime Holdings Insurance Services, Inc. (Prime)
Cash and Short-term Investments
Investment in unconsolidated investees	55,000		55,000
Other Unconsolidated Investees | Maximum
Cash and Short-term Investments
Investment in unconsolidated investees	1,000		1,000
FHLBC
Investment Holdings [Line Items]
Investments pledged as collateral	56,000		56,000
Federal home loan bank borrowings fair value disclosure	50,000		50,000
Investment In Low Income Housing Tax Credit Partnerships (LIHTC)
Investment Holdings [Line Items]
Other investments	12,000		12,000		13,000
Amortization on low income housing investments	800	$ 800	1,600	$ 1,700
Total tax benefit on investments in housing tax credit partnership	800	900	1,600	1,700
Qualified affordable housing project investments, unfunded commitment	1,000		1,000
Historic tax credit partnerships (HTC)
Investment Holdings [Line Items]
Other investments	15,000		15,000
Amortization on qualifying equity investments	1,100		2,300
Total tax benefit on investments in housing tax credit partnership	1,500	$ 1,300	2,900	$ 2,600
Equity investments in tax credit structures, unfunded commitment	4,000		4,000
Cash and Short-term Investments
Investment in unconsolidated investees					11,000
Investment in Private Funds
Investment Holdings [Line Items]
Other investments	27,000		27,000		$ 28,000
Fair value investments entities that calculate net asset value per share, unfunded commitments	$ 5,000		$ 5,000