Employee Benefit Plans (Pension and Post Retirement Asset Allocations in Accordance with Investment Guidelines) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Notional	$ 379,860	$ 405,644
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Total	13,906	12,807	$ 13,655
Net Value of investment of securities lending collateral invested in short-term bond	135	157
Liability for securities lending collateral	135	157
Pension Benefits | U.S. Equities
Defined Benefit Plan Disclosure [Line Items]
Total	475	518
Pension Benefits | U.S. Equities | Pooled separate accounts
Defined Benefit Plan Disclosure [Line Items]
Total	204	448
Pension Benefits | U.S. Equities | Common/collective trusts
Defined Benefit Plan Disclosure [Line Items]
Total	271	70
Pension Benefits | International Equities
Defined Benefit Plan Disclosure [Line Items]
Total	753	640
Pension Benefits | International Equities | Pooled separate accounts
Defined Benefit Plan Disclosure [Line Items]
Total	312	315
Pension Benefits | International Equities | Common/collective trusts
Defined Benefit Plan Disclosure [Line Items]
Total	393	283
Pension Benefits | International Equities | United Kingdom insurance pooled funds
Defined Benefit Plan Disclosure [Line Items]
Total	48	42
Pension Benefits | Fixed Maturities
Defined Benefit Plan Disclosure [Line Items]
Total	8,844	8,038
Pension Benefits | Fixed Maturities | Pooled separate accounts
Defined Benefit Plan Disclosure [Line Items]
Total	1,521	1,326
Pension Benefits | Fixed Maturities | Common/collective trusts
Defined Benefit Plan Disclosure [Line Items]
Total	521	485
Pension Benefits | Fixed Maturities | Mortgage-backed
Defined Benefit Plan Disclosure [Line Items]
Total	1	1
Pension Benefits | Fixed Maturities | Other U.S. government securities
Defined Benefit Plan Disclosure [Line Items]
Total	783	712
Pension Benefits | Fixed Maturities | U.S. government securities (state & other)
Defined Benefit Plan Disclosure [Line Items]
Total	562	519
Pension Benefits | Fixed Maturities | Non-U.S. government securities
Defined Benefit Plan Disclosure [Line Items]
Total	93	7
Pension Benefits | Fixed Maturities | United Kingdom insurance pooled funds
Defined Benefit Plan Disclosure [Line Items]
Total	90	289
Pension Benefits | Fixed Maturities | Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Total	4,281	3,478
Pension Benefits | Fixed Maturities | Asset-backed
Defined Benefit Plan Disclosure [Line Items]
Total	22	24
Pension Benefits | Fixed Maturities | Collateralized Mortgage Obligations
Defined Benefit Plan Disclosure [Line Items]
Total	485	474
Pension Benefits | Fixed Maturities | Other collateralized loans
Defined Benefit Plan Disclosure [Line Items]
Total	397	293
Pension Benefits | Fixed Maturities | Interest Rate Swaps
Defined Benefit Plan Disclosure [Line Items]
Notional	2,462	1,694
Total	2	11
Pension Benefits | Fixed Maturities | Variable Life Insurance Policies
Defined Benefit Plan Disclosure [Line Items]
Total		53
Pension Benefits | Fixed Maturities | Registered investment companies
Defined Benefit Plan Disclosure [Line Items]
Total	7	293
Pension Benefits | Fixed Maturities | Other
Defined Benefit Plan Disclosure [Line Items]
Total	79	73
Pension Benefits | Fixed Maturities | Unrealized gain (loss) on investment of securities lending collateral
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | Short-term Investments
Defined Benefit Plan Disclosure [Line Items]
Total	91	77
Pension Benefits | Short-term Investments | Pooled separate accounts
Defined Benefit Plan Disclosure [Line Items]
Total	61	74
Pension Benefits | Short-term Investments | United Kingdom insurance pooled funds
Defined Benefit Plan Disclosure [Line Items]
Total	30	3
Pension Benefits | Real Estate
Defined Benefit Plan Disclosure [Line Items]
Total	1,458	1,238
Pension Benefits | Real Estate | Pooled separate accounts
Defined Benefit Plan Disclosure [Line Items]
Total	770	760
Pension Benefits | Real Estate | Partnerships
Defined Benefit Plan Disclosure [Line Items]
Total	688	478
Pension Benefits | Other
Defined Benefit Plan Disclosure [Line Items]
Total	2,285	2,296
Pension Benefits | Other | Partnerships
Defined Benefit Plan Disclosure [Line Items]
Total	973	831
Pension Benefits | Other | Hedge Fund
Defined Benefit Plan Disclosure [Line Items]
Total	1,312	1,465
Pension Benefits | NAV Practical Expedient
Defined Benefit Plan Disclosure [Line Items]
Total	2,973	2,774
Pension Benefits | NAV Practical Expedient | U.S. Equities | Pooled separate accounts
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | NAV Practical Expedient | U.S. Equities | Common/collective trusts
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | NAV Practical Expedient | International Equities | Pooled separate accounts
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | NAV Practical Expedient | International Equities | Common/collective trusts
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | NAV Practical Expedient | International Equities | United Kingdom insurance pooled funds
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | NAV Practical Expedient | Fixed Maturities | Pooled separate accounts
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | NAV Practical Expedient | Fixed Maturities | Common/collective trusts
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | NAV Practical Expedient | Fixed Maturities | Mortgage-backed
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | NAV Practical Expedient | Fixed Maturities | Other U.S. government securities
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | NAV Practical Expedient | Fixed Maturities | U.S. government securities (state & other)
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | NAV Practical Expedient | Fixed Maturities | Non-U.S. government securities
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | NAV Practical Expedient | Fixed Maturities | United Kingdom insurance pooled funds
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | NAV Practical Expedient | Fixed Maturities | Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | NAV Practical Expedient | Fixed Maturities | Asset-backed
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | NAV Practical Expedient | Fixed Maturities | Collateralized Mortgage Obligations
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | NAV Practical Expedient | Fixed Maturities | Other collateralized loans
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | NAV Practical Expedient | Fixed Maturities | Interest Rate Swaps
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | NAV Practical Expedient | Fixed Maturities | Variable Life Insurance Policies
Defined Benefit Plan Disclosure [Line Items]
Total		0
Pension Benefits | NAV Practical Expedient | Fixed Maturities | Registered investment companies
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | NAV Practical Expedient | Fixed Maturities | Other
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | NAV Practical Expedient | Fixed Maturities | Unrealized gain (loss) on investment of securities lending collateral
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | NAV Practical Expedient | Short-term Investments | Pooled separate accounts
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | NAV Practical Expedient | Short-term Investments | United Kingdom insurance pooled funds
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | NAV Practical Expedient | Real Estate | Pooled separate accounts
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | NAV Practical Expedient | Real Estate | Partnerships
Defined Benefit Plan Disclosure [Line Items]
Total	688	478
Pension Benefits | NAV Practical Expedient | Other | Partnerships
Defined Benefit Plan Disclosure [Line Items]
Total	973	831
Pension Benefits | NAV Practical Expedient | Other | Hedge Fund
Defined Benefit Plan Disclosure [Line Items]
Total	1,312	1,465
Pension Benefits | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total	79	299
Pension Benefits | Level 1 | U.S. Equities | Pooled separate accounts
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | Level 1 | U.S. Equities | Common/collective trusts
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | Level 1 | International Equities | Pooled separate accounts
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | Level 1 | International Equities | Common/collective trusts
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | Level 1 | International Equities | United Kingdom insurance pooled funds
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | Level 1 | Fixed Maturities | Pooled separate accounts
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | Level 1 | Fixed Maturities | Common/collective trusts
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | Level 1 | Fixed Maturities | Mortgage-backed
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | Level 1 | Fixed Maturities | Other U.S. government securities
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | Level 1 | Fixed Maturities | U.S. government securities (state & other)
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | Level 1 | Fixed Maturities | Non-U.S. government securities
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | Level 1 | Fixed Maturities | United Kingdom insurance pooled funds
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | Level 1 | Fixed Maturities | Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | Level 1 | Fixed Maturities | Asset-backed
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | Level 1 | Fixed Maturities | Collateralized Mortgage Obligations
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | Level 1 | Fixed Maturities | Other collateralized loans
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | Level 1 | Fixed Maturities | Interest Rate Swaps
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | Level 1 | Fixed Maturities | Variable Life Insurance Policies
Defined Benefit Plan Disclosure [Line Items]
Total		0
Pension Benefits | Level 1 | Fixed Maturities | Registered investment companies
Defined Benefit Plan Disclosure [Line Items]
Total	7	293
Pension Benefits | Level 1 | Fixed Maturities | Other
Defined Benefit Plan Disclosure [Line Items]
Total	37	6
Pension Benefits | Level 1 | Fixed Maturities | Unrealized gain (loss) on investment of securities lending collateral
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | Level 1 | Short-term Investments | Pooled separate accounts
Defined Benefit Plan Disclosure [Line Items]
Total	5	0
Pension Benefits | Level 1 | Short-term Investments | United Kingdom insurance pooled funds
Defined Benefit Plan Disclosure [Line Items]
Total	30	0
Pension Benefits | Level 1 | Real Estate | Pooled separate accounts
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | Level 1 | Real Estate | Partnerships
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | Level 1 | Other | Partnerships
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | Level 1 | Other | Hedge Fund
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | Level 2
Defined Benefit Plan Disclosure [Line Items]
Total	10,040	8,910
Pension Benefits | Level 2 | U.S. Equities | Pooled separate accounts
Defined Benefit Plan Disclosure [Line Items]
Total	204	448
Pension Benefits | Level 2 | U.S. Equities | Common/collective trusts
Defined Benefit Plan Disclosure [Line Items]
Total	271	70
Pension Benefits | Level 2 | International Equities | Pooled separate accounts
Defined Benefit Plan Disclosure [Line Items]
Total	312	315
Pension Benefits | Level 2 | International Equities | Common/collective trusts
Defined Benefit Plan Disclosure [Line Items]
Total	393	283
Pension Benefits | Level 2 | International Equities | United Kingdom insurance pooled funds
Defined Benefit Plan Disclosure [Line Items]
Total	48	42
Pension Benefits | Level 2 | Fixed Maturities | Pooled separate accounts
Defined Benefit Plan Disclosure [Line Items]
Total	1,521	1,326
Pension Benefits | Level 2 | Fixed Maturities | Common/collective trusts
Defined Benefit Plan Disclosure [Line Items]
Total	521	485
Pension Benefits | Level 2 | Fixed Maturities | Mortgage-backed
Defined Benefit Plan Disclosure [Line Items]
Total	1	1
Pension Benefits | Level 2 | Fixed Maturities | Other U.S. government securities
Defined Benefit Plan Disclosure [Line Items]
Total	783	712
Pension Benefits | Level 2 | Fixed Maturities | U.S. government securities (state & other)
Defined Benefit Plan Disclosure [Line Items]
Total	562	519
Pension Benefits | Level 2 | Fixed Maturities | Non-U.S. government securities
Defined Benefit Plan Disclosure [Line Items]
Total	93	7
Pension Benefits | Level 2 | Fixed Maturities | United Kingdom insurance pooled funds
Defined Benefit Plan Disclosure [Line Items]
Total	90	289
Pension Benefits | Level 2 | Fixed Maturities | Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Total	4,281	3,476
Pension Benefits | Level 2 | Fixed Maturities | Asset-backed
Defined Benefit Plan Disclosure [Line Items]
Total	22	24
Pension Benefits | Level 2 | Fixed Maturities | Collateralized Mortgage Obligations
Defined Benefit Plan Disclosure [Line Items]
Total	485	474
Pension Benefits | Level 2 | Fixed Maturities | Other collateralized loans
Defined Benefit Plan Disclosure [Line Items]
Total	397	293
Pension Benefits | Level 2 | Fixed Maturities | Interest Rate Swaps
Defined Benefit Plan Disclosure [Line Items]
Total	2	11
Pension Benefits | Level 2 | Fixed Maturities | Variable Life Insurance Policies
Defined Benefit Plan Disclosure [Line Items]
Total		53
Pension Benefits | Level 2 | Fixed Maturities | Registered investment companies
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | Level 2 | Fixed Maturities | Other
Defined Benefit Plan Disclosure [Line Items]
Total	(2)	5
Pension Benefits | Level 2 | Fixed Maturities | Unrealized gain (loss) on investment of securities lending collateral
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | Level 2 | Short-term Investments | Pooled separate accounts
Defined Benefit Plan Disclosure [Line Items]
Total	56	74
Pension Benefits | Level 2 | Short-term Investments | United Kingdom insurance pooled funds
Defined Benefit Plan Disclosure [Line Items]
Total	0	3
Pension Benefits | Level 2 | Real Estate | Pooled separate accounts
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | Level 2 | Real Estate | Partnerships
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | Level 2 | Other | Partnerships
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | Level 2 | Other | Hedge Fund
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | Level 3
Defined Benefit Plan Disclosure [Line Items]
Total	814	824
Pension Benefits | Level 3 | U.S. Equities | Pooled separate accounts
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | Level 3 | U.S. Equities | Common/collective trusts
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | Level 3 | International Equities | Pooled separate accounts
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | Level 3 | International Equities | Common/collective trusts
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | Level 3 | International Equities | United Kingdom insurance pooled funds
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | Level 3 | Fixed Maturities | Pooled separate accounts
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | Level 3 | Fixed Maturities | Common/collective trusts
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | Level 3 | Fixed Maturities | Mortgage-backed
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | Level 3 | Fixed Maturities | Other U.S. government securities
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | Level 3 | Fixed Maturities | U.S. government securities (state & other)
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | Level 3 | Fixed Maturities | Non-U.S. government securities
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | Level 3 | Fixed Maturities | United Kingdom insurance pooled funds
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | Level 3 | Fixed Maturities | Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Total	0	2
Pension Benefits | Level 3 | Fixed Maturities | Asset-backed
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | Level 3 | Fixed Maturities | Collateralized Mortgage Obligations
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | Level 3 | Fixed Maturities | Other collateralized loans
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | Level 3 | Fixed Maturities | Interest Rate Swaps
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | Level 3 | Fixed Maturities | Variable Life Insurance Policies
Defined Benefit Plan Disclosure [Line Items]
Total		0
Pension Benefits | Level 3 | Fixed Maturities | Registered investment companies
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | Level 3 | Fixed Maturities | Other
Defined Benefit Plan Disclosure [Line Items]
Total	44	62
Pension Benefits | Level 3 | Fixed Maturities | Unrealized gain (loss) on investment of securities lending collateral
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | Level 3 | Short-term Investments | Pooled separate accounts
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | Level 3 | Short-term Investments | United Kingdom insurance pooled funds
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | Level 3 | Real Estate | Pooled separate accounts
Defined Benefit Plan Disclosure [Line Items]
Total	770	760
Pension Benefits | Level 3 | Real Estate | Partnerships
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | Level 3 | Other | Partnerships
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Pension Benefits | Level 3 | Other | Hedge Fund
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Total	1,557	1,432	$ 1,615
Other Postretirement Benefits | U.S. Equities
Defined Benefit Plan Disclosure [Line Items]
Total	771	644
Other Postretirement Benefits | U.S. Equities | Common/collective trusts
Defined Benefit Plan Disclosure [Line Items]
Total	83	75
Other Postretirement Benefits | U.S. Equities | Equities
Defined Benefit Plan Disclosure [Line Items]
Total		31
Other Postretirement Benefits | U.S. Equities | Variable Life Insurance Policies
Defined Benefit Plan Disclosure [Line Items]
Total	688	538
Other Postretirement Benefits | International Equities
Defined Benefit Plan Disclosure [Line Items]
Total	177	150
Other Postretirement Benefits | International Equities | Common/collective trusts
Defined Benefit Plan Disclosure [Line Items]
Total	59	53
Other Postretirement Benefits | International Equities | Equities
Defined Benefit Plan Disclosure [Line Items]
Total		6
Other Postretirement Benefits | International Equities | Variable Life Insurance Policies
Defined Benefit Plan Disclosure [Line Items]
Total	118	91
Other Postretirement Benefits | Fixed Maturities
Defined Benefit Plan Disclosure [Line Items]
Total	446	500
Other Postretirement Benefits | Fixed Maturities | Common/collective trusts
Defined Benefit Plan Disclosure [Line Items]
Total	131	130
Other Postretirement Benefits | Fixed Maturities | Other U.S. government securities
Defined Benefit Plan Disclosure [Line Items]
Total	20	25
Other Postretirement Benefits | Fixed Maturities | Non-U.S. government securities
Defined Benefit Plan Disclosure [Line Items]
Total	2
Other Postretirement Benefits | Fixed Maturities | Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Total	53	120
Other Postretirement Benefits | Fixed Maturities | Asset-backed
Defined Benefit Plan Disclosure [Line Items]
Total	15	27
Other Postretirement Benefits | Fixed Maturities | Collateralized Mortgage Obligations
Defined Benefit Plan Disclosure [Line Items]
Total	10	18
Other Postretirement Benefits | Fixed Maturities | Other collateralized loans
Defined Benefit Plan Disclosure [Line Items]
Total	16	18
Other Postretirement Benefits | Fixed Maturities | Interest Rate Swaps
Defined Benefit Plan Disclosure [Line Items]
Notional	253	188
Total	0	(1)
Other Postretirement Benefits | Fixed Maturities | Variable Life Insurance Policies
Defined Benefit Plan Disclosure [Line Items]
Total	194	157
Other Postretirement Benefits | Fixed Maturities | Registered investment companies
Defined Benefit Plan Disclosure [Line Items]
Total	4	3
Other Postretirement Benefits | Fixed Maturities | Other
Defined Benefit Plan Disclosure [Line Items]
Total	1	3
Other Postretirement Benefits | Short-term Investments
Defined Benefit Plan Disclosure [Line Items]
Total	163	138
Other Postretirement Benefits | Short-term Investments | Registered investment companies
Defined Benefit Plan Disclosure [Line Items]
Total	163	138
Other Postretirement Benefits | NAV Practical Expedient
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Other Postretirement Benefits | NAV Practical Expedient | U.S. Equities | Common/collective trusts
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Other Postretirement Benefits | NAV Practical Expedient | U.S. Equities | Equities
Defined Benefit Plan Disclosure [Line Items]
Total		0
Other Postretirement Benefits | NAV Practical Expedient | U.S. Equities | Variable Life Insurance Policies
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Other Postretirement Benefits | NAV Practical Expedient | International Equities | Common/collective trusts
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Other Postretirement Benefits | NAV Practical Expedient | International Equities | Equities
Defined Benefit Plan Disclosure [Line Items]
Total		0
Other Postretirement Benefits | NAV Practical Expedient | International Equities | Variable Life Insurance Policies
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Other Postretirement Benefits | NAV Practical Expedient | Fixed Maturities | Common/collective trusts
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Other Postretirement Benefits | NAV Practical Expedient | Fixed Maturities | Other U.S. government securities
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Other Postretirement Benefits | NAV Practical Expedient | Fixed Maturities | Non-U.S. government securities
Defined Benefit Plan Disclosure [Line Items]
Total	0
Other Postretirement Benefits | NAV Practical Expedient | Fixed Maturities | Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Other Postretirement Benefits | NAV Practical Expedient | Fixed Maturities | Asset-backed
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Other Postretirement Benefits | NAV Practical Expedient | Fixed Maturities | Collateralized Mortgage Obligations
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Other Postretirement Benefits | NAV Practical Expedient | Fixed Maturities | Other collateralized loans
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Other Postretirement Benefits | NAV Practical Expedient | Fixed Maturities | Interest Rate Swaps
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Other Postretirement Benefits | NAV Practical Expedient | Fixed Maturities | Variable Life Insurance Policies
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Other Postretirement Benefits | NAV Practical Expedient | Fixed Maturities | Registered investment companies
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Other Postretirement Benefits | NAV Practical Expedient | Fixed Maturities | Other
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Other Postretirement Benefits | NAV Practical Expedient | Short-term Investments | Registered investment companies
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Other Postretirement Benefits | Level 1
Defined Benefit Plan Disclosure [Line Items]
Total	167	166
Other Postretirement Benefits | Level 1 | U.S. Equities | Common/collective trusts
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Other Postretirement Benefits | Level 1 | U.S. Equities | Equities
Defined Benefit Plan Disclosure [Line Items]
Total		25
Other Postretirement Benefits | Level 1 | U.S. Equities | Variable Life Insurance Policies
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Other Postretirement Benefits | Level 1 | International Equities | Common/collective trusts
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Other Postretirement Benefits | Level 1 | International Equities | Equities
Defined Benefit Plan Disclosure [Line Items]
Total		0
Other Postretirement Benefits | Level 1 | International Equities | Variable Life Insurance Policies
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Other Postretirement Benefits | Level 1 | Fixed Maturities | Common/collective trusts
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Other Postretirement Benefits | Level 1 | Fixed Maturities | Other U.S. government securities
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Other Postretirement Benefits | Level 1 | Fixed Maturities | Non-U.S. government securities
Defined Benefit Plan Disclosure [Line Items]
Total	0
Other Postretirement Benefits | Level 1 | Fixed Maturities | Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Other Postretirement Benefits | Level 1 | Fixed Maturities | Asset-backed
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Other Postretirement Benefits | Level 1 | Fixed Maturities | Collateralized Mortgage Obligations
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Other Postretirement Benefits | Level 1 | Fixed Maturities | Other collateralized loans
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Other Postretirement Benefits | Level 1 | Fixed Maturities | Interest Rate Swaps
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Other Postretirement Benefits | Level 1 | Fixed Maturities | Variable Life Insurance Policies
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Other Postretirement Benefits | Level 1 | Fixed Maturities | Registered investment companies
Defined Benefit Plan Disclosure [Line Items]
Total	4	3
Other Postretirement Benefits | Level 1 | Fixed Maturities | Other
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Other Postretirement Benefits | Level 1 | Short-term Investments | Registered investment companies
Defined Benefit Plan Disclosure [Line Items]
Total	163	138
Other Postretirement Benefits | Level 2
Defined Benefit Plan Disclosure [Line Items]
Total	1,389	1,261
Other Postretirement Benefits | Level 2 | U.S. Equities | Common/collective trusts
Defined Benefit Plan Disclosure [Line Items]
Total	83	75
Other Postretirement Benefits | Level 2 | U.S. Equities | Equities
Defined Benefit Plan Disclosure [Line Items]
Total		6
Other Postretirement Benefits | Level 2 | U.S. Equities | Variable Life Insurance Policies
Defined Benefit Plan Disclosure [Line Items]
Total	688	538
Other Postretirement Benefits | Level 2 | International Equities | Common/collective trusts
Defined Benefit Plan Disclosure [Line Items]
Total	59	53
Other Postretirement Benefits | Level 2 | International Equities | Equities
Defined Benefit Plan Disclosure [Line Items]
Total		6
Other Postretirement Benefits | Level 2 | International Equities | Variable Life Insurance Policies
Defined Benefit Plan Disclosure [Line Items]
Total	118	91
Other Postretirement Benefits | Level 2 | Fixed Maturities | Common/collective trusts
Defined Benefit Plan Disclosure [Line Items]
Total	131	130
Other Postretirement Benefits | Level 2 | Fixed Maturities | Other U.S. government securities
Defined Benefit Plan Disclosure [Line Items]
Total	20	25
Other Postretirement Benefits | Level 2 | Fixed Maturities | Non-U.S. government securities
Defined Benefit Plan Disclosure [Line Items]
Total	2
Other Postretirement Benefits | Level 2 | Fixed Maturities | Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Total	53	120
Other Postretirement Benefits | Level 2 | Fixed Maturities | Asset-backed
Defined Benefit Plan Disclosure [Line Items]
Total	15	26
Other Postretirement Benefits | Level 2 | Fixed Maturities | Collateralized Mortgage Obligations
Defined Benefit Plan Disclosure [Line Items]
Total	10	17
Other Postretirement Benefits | Level 2 | Fixed Maturities | Other collateralized loans
Defined Benefit Plan Disclosure [Line Items]
Total	16	18
Other Postretirement Benefits | Level 2 | Fixed Maturities | Interest Rate Swaps
Defined Benefit Plan Disclosure [Line Items]
Total	0	(1)
Other Postretirement Benefits | Level 2 | Fixed Maturities | Variable Life Insurance Policies
Defined Benefit Plan Disclosure [Line Items]
Total	194	157
Other Postretirement Benefits | Level 2 | Fixed Maturities | Registered investment companies
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Other Postretirement Benefits | Level 2 | Fixed Maturities | Other
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Other Postretirement Benefits | Level 2 | Short-term Investments | Registered investment companies
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Other Postretirement Benefits | Level 3
Defined Benefit Plan Disclosure [Line Items]
Total	1	5
Other Postretirement Benefits | Level 3 | U.S. Equities | Common/collective trusts
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Other Postretirement Benefits | Level 3 | U.S. Equities | Equities
Defined Benefit Plan Disclosure [Line Items]
Total		0
Other Postretirement Benefits | Level 3 | U.S. Equities | Variable Life Insurance Policies
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Other Postretirement Benefits | Level 3 | International Equities | Common/collective trusts
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Other Postretirement Benefits | Level 3 | International Equities | Equities
Defined Benefit Plan Disclosure [Line Items]
Total		0
Other Postretirement Benefits | Level 3 | International Equities | Variable Life Insurance Policies
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Other Postretirement Benefits | Level 3 | Fixed Maturities | Common/collective trusts
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Other Postretirement Benefits | Level 3 | Fixed Maturities | Other U.S. government securities
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Other Postretirement Benefits | Level 3 | Fixed Maturities | Non-U.S. government securities
Defined Benefit Plan Disclosure [Line Items]
Total	0
Other Postretirement Benefits | Level 3 | Fixed Maturities | Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Other Postretirement Benefits | Level 3 | Fixed Maturities | Asset-backed
Defined Benefit Plan Disclosure [Line Items]
Total	0	1
Other Postretirement Benefits | Level 3 | Fixed Maturities | Collateralized Mortgage Obligations
Defined Benefit Plan Disclosure [Line Items]
Total	0	1
Other Postretirement Benefits | Level 3 | Fixed Maturities | Other collateralized loans
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Other Postretirement Benefits | Level 3 | Fixed Maturities | Interest Rate Swaps
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Other Postretirement Benefits | Level 3 | Fixed Maturities | Variable Life Insurance Policies
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Other Postretirement Benefits | Level 3 | Fixed Maturities | Registered investment companies
Defined Benefit Plan Disclosure [Line Items]
Total	0	0
Other Postretirement Benefits | Level 3 | Fixed Maturities | Other
Defined Benefit Plan Disclosure [Line Items]
Total	1	3
Other Postretirement Benefits | Level 3 | Short-term Investments | Registered investment companies
Defined Benefit Plan Disclosure [Line Items]
Total	$ 0	$ 0