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	$ 292,418	$ 274,026
Liabilities	(25,625)	(19,925)
Fair Value | Mortgage loans on real estate
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets	21,246	19,523
Fair Value | Other investments – short-term investments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets	6,087	6,272
Fair Value | Policy loans
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets	2,574	2,465
Fair Value | Cash and invested cash
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets	9,944	4,505
Fair Value | Policyholder account balances – certain investment contracts and other liabilities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liabilities	(36,351)	(29,689)
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	(105)	(24)
Fair Value | Long-term debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liabilities	(2,202)	(2,164)
Fair Value | Funds withheld reinsurance-related liabilities – excluding embedded derivatives
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liabilities	(29,798)	(27,538)
Carrying Value | Mortgage loans on real estate
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets	21,862	20,940
Carrying Value | Other investments – short-term investments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets	6,087	6,272
Carrying Value | Policy loans
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets	2,574	2,465
Carrying Value | Cash and invested cash
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets	9,944	4,505
Carrying Value | Policyholder account balances – certain investment contracts and other liabilities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liabilities	(43,183)	(39,137)
Carrying Value | Policyholder account balances – funding agreements
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liabilities	(1,892)
Carrying Value | Short-term debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liabilities	(105)	(24)
Carrying Value | Long-term debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liabilities	(2,147)	(2,173)
Carrying Value | Funds withheld reinsurance-related liabilities – excluding embedded derivatives
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liabilities	(29,798)	(27,538)
Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets	1,222	808
Liabilities	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 – short-term 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 – certain investment contracts 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	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	272,467	256,411
Liabilities	(6,549)	(3,469)
Significant Observable Inputs (Level 2) | Fair Value | Mortgage loans on real estate
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets	21,246	19,523
Significant Observable Inputs (Level 2) | Fair Value | Other investments – short-term investments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets	598	1,061
Significant Observable Inputs (Level 2) | Fair Value | Policy loans
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets	2,574	2,465
Significant Observable Inputs (Level 2) | Fair Value | Cash and invested cash
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets	9,944	4,505
Significant Observable Inputs (Level 2) | Fair Value | Policyholder account balances – certain investment contracts 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	(105)	(24)
Significant Observable Inputs (Level 2) | Fair Value | Long-term debt
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liabilities	(2,202)	(2,164)
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	18,729	16,807
Liabilities	(19,076)	(16,456)
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 – short-term investments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets	5,489	5,211
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 – certain investment contracts and other liabilities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Liabilities	(36,351)	(29,689)
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	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	$ (29,798)	$ (27,538)