Borrowings and Financing Activities - Narrative (Details) - USD ($)	1 Months Ended	3 Months Ended		6 Months Ended
	Mar. 31, 2024	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	May 31, 2024	Apr. 30, 2024	Jan. 31, 2024	Dec. 31, 2023
Debt Instrument [Line Items]
Repayments in cash				$ 527,079,000	$ 0
Loss on extinguishment of debt		$ 0	$ 0	4,275,000	$ 0
Collateral		6,588,149,000		6,588,149,000					$ 6,085,654,000
Mortgage loans held for sale | Asset Pledged as Collateral
Debt Instrument [Line Items]
Collateral		456,000,000		456,000,000					31,000,000
Total fixed-maturities available for sale | Fixed maturities AFS and trading securities
Debt Instrument [Line Items]
FHLB, collateral pledged		66,000,000		66,000,000					101,000,000
Senior notes
Debt Instrument [Line Items]
Outstanding borrowings		1,513,782,000		$ 1,513,782,000					1,417,781,000
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 | Flagstar Bank Master Repurchase Agreement
Debt Instrument [Line Items]
Maximum borrowing capacity								$ 150,000,000
Revolving Credit Facility
Debt Instrument [Line Items]
Fair value of amount outstanding		0		$ 0
Revolving Credit Facility | Unsecured Revolving Credit Facility, Expiration Date 2026
Debt Instrument [Line Items]
Current borrowing capacity		$ 275,000,000		$ 275,000,000
Senior Notes due 2029 | Senior notes
Debt Instrument [Line Items]
Aggregate principal amount	$ 625,000,000
Net proceeds received	$ 617,000,000
Interest rate on senior notes		6.20%		6.20%
Basis spread on variable rate				0.30%
Redemption price, percentage of principal amount				100.00%
Stock retention percentage required in order to make capital stock transactions		80.00%		80.00%
Outstanding borrowings		$ 617,183,000		$ 617,183,000					0
Senior Notes due 2025 | Senior notes
Debt Instrument [Line Items]
Interest rate on senior notes		6.625%		6.625%
Redemption price, percentage of principal amount	100.40%
Aggregate principal redemption amount	$ 525,000,000
Repayments in cash	527,000,000
Loss on extinguishment of debt	$ 4,000,000
Outstanding borrowings		$ 0		$ 0					$ 522,343,000