Fair Value Measurements - Financial Instruments Not Carried at Fair Value (Details) - USD ($) $ in Millions	Mar. 31, 2020	Jan. 01, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, carrying value	$ 68,724		$ 70,817
Assets, fair value	43,883		46,749
Liabilities, carrying value	53,458		54,547
Financing Receivable, Allowance for Credit Loss		$ 19	0
Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value	1,402		1,502
Significant Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value	39,915		42,488
Carrying Amount | Significant Unobservable Inputs (Level 3) | Other policyholder funds and benefits payable
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities, carrying value	766		763
Carrying Amount | Significant Unobservable Inputs (Level 3) | Mortgage loans (net of ACL of $21 and $0)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, carrying value	4,353		4,215
Carrying Amount | Significant Observable Inputs (Level 2) | Senior notes [1]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities, carrying value	3,260		3,759
Carrying Amount | Significant Observable Inputs (Level 2) | Junior subordinated debentures [1]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities, carrying value	1,089		1,089
Fair Value | Significant Unobservable Inputs (Level 3) | Other policyholder funds and benefits payable
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities, fair value	768		765
Fair Value | Significant Unobservable Inputs (Level 3) | Mortgage loans (net of ACL of $21 and $0)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value	4,341		4,350
Fair Value | Significant Observable Inputs (Level 2) | Senior notes [1]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities, fair value	3,706		4,456
Fair Value | Significant Observable Inputs (Level 2) | Junior subordinated debentures [1]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities, fair value	962		1,153
Commercial Loan [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financing Receivable, Allowance for Credit Loss	$ 21		$ 0	$ 1	$ 1