Insurance (Liabilities for Unpaid Claims - Methodology) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Liability for Claims and Claims Adjustment Expense [Line Items]
Short-duration Insurance Contract, Discounted Liability, Discount	$ 1,285
Group Long-Term Disability
Liability for Claims and Claims Adjustment Expense [Line Items]
Short-Duration Contracts, Discounted Liabilities, Amount	6,000	$ 6,000
Short-duration Insurance Contract, Discounted Liability, Discount	1,200	1,300
Short-duration Insurance Contracts, Discounted Liabilities, Interest Accretion	$ 470	509	$ 510
Group Long-Term Disability | Minimum
Liability for Claims and Claims Adjustment Expense [Line Items]
Short-Duration Contract, Discounted Liability, Discount Rate	3.00%
Group Long-Term Disability | Maximum
Liability for Claims and Claims Adjustment Expense [Line Items]
Short-Duration Contract, Discounted Liability, Discount Rate	8.00%
Group Life - Term | Asia
Liability for Claims and Claims Adjustment Expense [Line Items]
Short-Duration Contracts, Discounted Liabilities, Amount	$ 814	733
Short-duration Insurance Contract, Discounted Liability, Discount	52	61
Short-duration Insurance Contracts, Discounted Liabilities, Interest Accretion	$ 20	$ 19	$ 26
Group Life - Term | Minimum | Asia
Liability for Claims and Claims Adjustment Expense [Line Items]
Short-Duration Contract, Discounted Liability, Discount Rate	1.00%
Group Life - Term | Maximum | Asia
Liability for Claims and Claims Adjustment Expense [Line Items]
Short-Duration Contract, Discounted Liability, Discount Rate	7.00%