Borrowings and Financing Activities - Additional Information (Details)	3 Months Ended
	Mar. 31, 2025 USD ($)	Mar. 31, 2024 USD ($)	Dec. 31, 2024 USD ($)	May 31, 2024 USD ($)	Apr. 30, 2024 USD ($)	Jan. 31, 2024 USD ($)
Debt Instrument [Line Items]
Repayments in cash	$ 0	$ 527,079,000
Loss on extinguishment of debt	0	$ 4,275,000
Collateral	6,113,792,000		$ 6,345,236,000
Residential mortgage loans held for sale | Asset Pledged as Collateral
Debt Instrument [Line Items]
Collateral	271,000,000		515,000,000
Total fixed-maturities available for sale | Fixed maturities AFS and trading securities
Debt Instrument [Line Items]
FHLB, collateral pledged	34,000,000		49,000,000
Senior Notes
Debt Instrument [Line Items]
Outstanding borrowings	$ 1,065,965,000		1,065,337,000
FHLB Advances | Minimum
Debt Instrument [Line Items]
FHLB, ratio of market value of collateral to advances	1.03
FHLB Advances | Maximum
Debt Instrument [Line Items]
FHLB, ratio of market value of collateral to advances	1.14
Mortgage Loan Financing Facilities | Goldman Sachs Master Repurchase Agreement
Debt Instrument [Line Items]
Maximum borrowing capacity				$ 200,000,000
Mortgage Loan Financing Facilities | BMO Master Repurchase Agreement
Debt Instrument [Line Items]
Maximum borrowing capacity					$ 400,000,000
Mortgage Loan Financing Facilities | JP Morgan Master Repurchase Agreement
Debt Instrument [Line Items]
Maximum borrowing capacity						$ 300,000,000
Revolving Credit Facility
Debt Instrument [Line Items]
Fair value of amount outstanding	$ 0
Revolving Credit Facility | Unsecured Revolving Credit Facility, Expiration Date 2026
Debt Instrument [Line Items]
Current borrowing capacity	$ 275,000,000
Senior Notes due 2029 | Senior Notes
Debt Instrument [Line Items]
Interest rate on senior notes	6.20%
Outstanding borrowings	$ 618,231,000		$ 617,876,000