Investments - Narrative (Details) - USD ($)	6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Dec. 31, 2024
Debt Securities, Available-for-sale [Line Items]
Mortgage- and Asset-backed Securities Not Due at a Single Maturity Date	$ 1,712,700,000
Financing Receivable, Accrued Interest, before Allowance for Credit Loss	73,500,000		$ 70,900,000
Equity securities, FV-NI, unrealized gain (loss)	$ (100,000)	$ (600,000)
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	2.10%
Loans to Policyholders	$ 278,600,000		280,700,000
Equity Securities at Modified Cost	22,200,000		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	0	$ 400,000
Alternative Energy Partnership Investments
Debt Securities, Available-for-sale [Line Items]
Alternative Energy Partnership Investments	17,400,000		17,600,000
Investments in Fixed Maturities
Debt Securities, Available-for-sale [Line Items]
Other Receivables	6,100,000		1,800,000
Other liabilities	96,900,000		11,600,000
Debt securities, available-for-sale, unrealized loss position, accumulated loss	828,700,000		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	302,200,000
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	96,400,000
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	73,800,000
Other Non-Governmental Issuers
Debt Securities, Available-for-sale [Line Items]
Mortgage- and Asset-backed Securities Not Due at a Single Maturity Date	1,240,300,000
Equity Securities
Debt Securities, Available-for-sale [Line Items]
Other Receivables			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	192,900,000		185,700,000
Equity Securities, FV-NI, Current	284,100,000		218,500,000
Alternative Energy Partnership Investments	176,200,000		186,300,000
Loans to Policyholders	278,600,000		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	89,000,000.0
Investment grade | Investments in Fixed Maturities
Debt Securities, Available-for-sale [Line Items]
Debt securities, available-for-sale, unrealized loss position, accumulated loss	808,900,000		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	$ 19,800,000		$ 14,200,000
Percentage of unrealized loss position to amortized cost basis of available for sale security average	7.80%		4.90%