Investments - Narrative (Details) - USD ($)	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Dec. 31, 2024
Debt Securities, Available-for-sale [Line Items]
Mortgage- and Asset-backed Securities Not Due at a Single Maturity Date	$ 1,573,300,000
Financing Receivable, Accrued Interest, before Allowance for Credit Loss	68,600,000		$ 70,900,000
Equity securities, FV-NI, unrealized gain (loss)	$ (500,000)	$ 3,900,000
Percentage of Equity Method Limited Liability Investments reported with a lag	2.90%
Percentage of Equity Method Limited Liability Investments reported with a One Month Lag	3.70%
Loans to Policyholders	$ 279,800,000		280,700,000
Equity Securities at Modified Cost	21,700,000		22,500,000
Equity securities without readily determinable fair value, impairment loss, cumulative amount	3,200,000		3,200,000
Equity Securities
Debt Securities, Available-for-sale [Line Items]
Other Asset Impairment Charges		$ 400,000
Alternative Energy Partnership Investments
Debt Securities, Available-for-sale [Line Items]
Alternative Energy Partnership Investments	17,300,000		17,600,000
Investments in Fixed Maturities
Debt Securities, Available-for-sale [Line Items]
Other Receivables	3,900,000		1,800,000
Other liabilities	60,000,000.0		11,600,000
Debt securities, available-for-sale, unrealized loss position, accumulated loss	821,700,000		889,500,000
Government National Mortgage Association Certificates and Obligations (GNMA)
Debt Securities, Available-for-sale [Line Items]
Mortgage- and Asset-backed Securities Not Due at a Single Maturity Date	217,900,000
Federal National Mortgage Association Certificates and Obligations (FNMA)
Debt Securities, Available-for-sale [Line Items]
Mortgage- and Asset-backed Securities Not Due at a Single Maturity Date	99,500,000
Federal Home Loan Mortgage Corporation Certificates and Obligations (FHLMC)
Debt Securities, Available-for-sale [Line Items]
Mortgage- and Asset-backed Securities Not Due at a Single Maturity Date	76,000,000.0
Other Non-Governmental Issuers
Debt Securities, Available-for-sale [Line Items]
Mortgage- and Asset-backed Securities Not Due at a Single Maturity Date	1,179,900,000
Equity Securities
Debt Securities, Available-for-sale [Line Items]
Other Receivables	100,000		300,000
Other liabilities	0		0
Equity Method Investments
Debt Securities, Available-for-sale [Line Items]
Other liabilities	0		0
Consolidated Entity, Excluding VIE
Debt Securities, Available-for-sale [Line Items]
Other Receivables	189,200,000		185,700,000
Equity Securities, FV-NI, Current	232,300,000		218,500,000
Alternative Energy Partnership Investments	185,100,000		186,300,000
Loans to Policyholders	279,800,000		280,700,000
Variable Interest Entity, Not Primary Beneficiary | Equity Method Limited Liability Investments
Debt Securities, Available-for-sale [Line Items]
Outstanding commitments to fund equity method limited liability investments	91,800,000
Investment grade | Investments in Fixed Maturities
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale, unrealized loss position, accumulated loss	807,700,000		875,300,000
Non-investment-grade | Investments in Fixed Maturities
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale, unrealized loss position, accumulated loss	$ 14,000,000.0		$ 14,200,000
Percentage of unrealized loss position to amortized cost basis of available for sale security average	3.70%		4.90%