Insurance (Reconciliation of Disclosure to Liability) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
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	$ 12,644
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	910
Total unpaid claims and allocated claims adjustment expense	13,554
Unallocated claims adjustment expenses	2
Discounting	(1,254)
Liability for unpaid claims and claim adjustment liabilities - short-duration	12,302
Liability for unpaid claims and claim adjustment liabilities - long-duration	6,289
Liability for Claims and Claims Adjustment Expense	18,591	$ 19,216	$ 17,788	$ 17,094
UNITED STATES
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	9,351
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	140
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	510
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	20
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	2,372
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	12
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	792
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	313
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	6,979
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	128
Discounting	(1,200)	$ (1,200)
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	404
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	8
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	106
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	12
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	1,991
Reinsurance Recoverable for Unpaid Claims and Claims Adjustments	$ 437