Insurance (Reconciliation of Disclosure to Liability) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net	$ 12,575
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	778
Total unpaid claims and allocated claims adjustment expense	13,353
Unallocated claims adjustment expenses	90
Discounting	(1,314)
Liability for unpaid claims and claim adjustment liabilities - short-duration	12,129
Liability for unpaid claims and claim adjustment liabilities - long-duration	5,659
Liability for Claims and Claims Adjustment Expense	17,788	$ 17,094	$ 16,157	$ 9,669
U.S.
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net	10,509
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	199
Latin America
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net	381
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	10
Group Life - Term
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net	2,012
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	20
Group Life - Term | Asia
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net	578
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	216
Group Long-Term Disability
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net	7,112
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	109
Discounting	(1,300)	$ (1,300)
Property & Casualty - Auto
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net	1,160
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	66
Property & Casualty - Home
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net	225
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	4
Protection Life
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net	308
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	4
Protection Health
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net	73
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	6
Other insurance lines - all segments combined
Short-duration Insurance Contracts, Reconciliation of Claims Development to Liability [Line Items]
Short-duration Insurance Contracts, Liability for Unpaid Claims and Allocated Claim Adjustment Expense, Net	1,107
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	$ 353