Fair Value of Financial Instruments - Carrying and Estimated Fair Values of Financial Instruments (Details) - USD ($) $ in Millions	Sep. 30, 2025	Dec. 31, 2024
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets	$ 296,727	$ 278,356
Liabilities	(23,836)	(18,301)
Mortgage loans on real estate
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets	230	232
Other investments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets	222	392
Fair Value | Mortgage loans on real estate
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets	21,375	19,647
Fair Value | Other investments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets	6,383	6,588
Fair Value | Policy loans
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets	2,584	2,476
Fair Value | Cash and invested cash
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets	10,668	5,801
Fair Value | Policyholder account balances and other liabilities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liabilities	(36,352)	(30,505)
Fair Value | Policyholder account balances – funding agreements
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liabilities	(1,942)
Fair Value | Short-term debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liabilities		(299)
Fair Value | Long-term Debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liabilities	(5,497)	(5,304)
Fair Value | Funds withheld reinsurance-related liabilities – excluding embedded derivatives
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liabilities	(17,205)	(16,877)
Carrying Amount | Mortgage loans on real estate
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets	22,000	21,083
Carrying Amount | Other investments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets	6,383	6,588
Carrying Amount | Policy loans
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets	2,584	2,476
Carrying Amount | Cash and invested cash
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets	10,668	5,801
Carrying Amount | Policyholder account balances and other liabilities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liabilities	(43,203)	(40,394)
Carrying Amount | Policyholder account balances – funding agreements
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liabilities	(1,892)
Carrying Amount | Short-term debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liabilities		(300)
Carrying Amount | Long-term Debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liabilities	(5,772)	(5,856)
Carrying Amount | Funds withheld reinsurance-related liabilities – excluding embedded derivatives
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liabilities	(17,205)	(16,877)
Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets	1,224	810
Liabilities	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Mortgage loans on real estate
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Other investments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value | Mortgage loans on real estate
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value | Other investments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value | Policy loans
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value | Cash and invested cash
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value | Policyholder account balances and other liabilities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liabilities	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value | Policyholder account balances – funding agreements
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liabilities	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value | Short-term debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liabilities		0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value | Long-term Debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liabilities	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value | Funds withheld reinsurance-related liabilities – excluding embedded derivatives
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liabilities	0	0
Significant Observable Inputs (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets	282,068	265,955
Liabilities	(6,735)	(4,052)
Significant Observable Inputs (Level 2) | Mortgage loans on real estate
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets	0	0
Significant Observable Inputs (Level 2) | Other investments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets	214	369
Significant Observable Inputs (Level 2) | Fair Value | Mortgage loans on real estate
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets	21,375	19,647
Significant Observable Inputs (Level 2) | Fair Value | Other investments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets	659	1,119
Significant Observable Inputs (Level 2) | Fair Value | Policy loans
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets	2,584	2,476
Significant Observable Inputs (Level 2) | Fair Value | Cash and invested cash
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets	10,668	5,801
Significant Observable Inputs (Level 2) | Fair Value | Policyholder account balances and other liabilities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liabilities	0	0
Significant Observable Inputs (Level 2) | Fair Value | Policyholder account balances – funding agreements
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liabilities	(1,942)
Significant Observable Inputs (Level 2) | Fair Value | Short-term debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liabilities		(299)
Significant Observable Inputs (Level 2) | Fair Value | Long-term Debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liabilities	(5,497)	(5,304)
Significant Observable Inputs (Level 2) | Fair Value | Funds withheld reinsurance-related liabilities – excluding embedded derivatives
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liabilities	0	0
Significant Unobservable Inputs (Level 3)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets	13,435	11,591
Liabilities	(17,101)	(14,249)
Significant Unobservable Inputs (Level 3) | Mortgage loans on real estate
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets	230	232
Significant Unobservable Inputs (Level 3) | Other investments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets	8	23
Significant Unobservable Inputs (Level 3) | Fair Value | Mortgage loans on real estate
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets	0	0
Significant Unobservable Inputs (Level 3) | Fair Value | Other investments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets	5,724	5,469
Significant Unobservable Inputs (Level 3) | Fair Value | Policy loans
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets	0	0
Significant Unobservable Inputs (Level 3) | Fair Value | Cash and invested cash
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets	0	0
Significant Unobservable Inputs (Level 3) | Fair Value | Policyholder account balances and other liabilities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liabilities	(36,352)	(30,505)
Significant Unobservable Inputs (Level 3) | Fair Value | Policyholder account balances – funding agreements
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liabilities	0
Significant Unobservable Inputs (Level 3) | Fair Value | Short-term debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liabilities		0
Significant Unobservable Inputs (Level 3) | Fair Value | Long-term Debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liabilities	0	0
Significant Unobservable Inputs (Level 3) | Fair Value | Funds withheld reinsurance-related liabilities – excluding embedded derivatives
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liabilities	$ (17,205)	$ (16,877)