Investments - Debt and Short-term Investments (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
Investment Holdings [Line Items]
Other investments	$ 48,837		$ 48,837		$ 50,501
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	$ 58,105		$ 58,105		$ 171,311
Cash	723,511		723,511		88,804
Prime Holdings Insurance Services, Inc. (Prime)
Cash and Short-term Investments
Investment in unconsolidated investees	46,900		46,900
Other Unconsolidated Investees
Cash and Short-term Investments
Investment in unconsolidated investees	11,200		11,200
Unfunded commitments	7,700		7,700
FHLBC
Investment Holdings [Line Items]
Investments pledged as collateral	60,200		60,200
Federal home loan bank borrowings fair value disclosure	50,000		50,000
Investment In Low Income Housing Tax Credit Partnership Net Of Amortization
Investment Holdings [Line Items]
Other investments	14,200		14,200		16,600
Total tax benefit on investments in housing tax credit partnership	900	$ 900	2,600	$ 2,700
Qualified affordable housing project investments, commitment	1,300		1,300
Investment in Private Funds
Investment Holdings [Line Items]
Other investments	28,900		28,900		$ 28,600
Fair value investments entities that calculate net asset value per share unfunded commitments	$ 5,700		$ 5,700