Investments - Debt and Short-term Investments (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Investment Holdings [Line Items]
Other investments	$ 52,849,000		$ 52,849,000		$ 54,232,000
Investment in federal home loan bank stock	us-gaap:AssetPledgedAsCollateralMember		us-gaap:AssetPledgedAsCollateralMember		us-gaap:AssetPledgedAsCollateralMember
Cash and Short-term Investments
Cash	$ 95,457,000		$ 95,457,000		$ 62,217,000
FHLBC
Investment Holdings [Line Items]
Investments pledged as collateral	9,600,000		9,600,000
Federal home loan bank borrowings fair value disclosure	0		0
Investment In Low Income Housing Tax Credit Partnership Net Of Amortization
Investment Holdings [Line Items]
Other investments	18,300,000		18,300,000		20,300,000
Total tax benefit on investments in housing tax credit partnership	900,000	$ 900,000	1,800,000	$ 1,800,000
Qualified affordable housing project investments, commitment	2,400,000		2,400,000
Investment in Private Funds
Investment Holdings [Line Items]
Other investments	31,100,000		31,100,000		$ 32,100,000
Fair value investments entities that calculate net asset value per share unfunded commitments	$ 9,300,000		$ 9,300,000