Segment Information (Premiums, Universal Life and Investment-Type Policy Fees and Other Revenues by Major Product Groups) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Total premiums, universal life and investment-type product policy fees and other revenues	$ 45,843	$ 44,370	$ 43,900
Life insurance (1)
Segment Reporting Information [Line Items]
Total premiums, universal life and investment-type product policy fees and other revenues	20,330	20,436	20,847
Accident & health insurance
Segment Reporting Information [Line Items]
Total premiums, universal life and investment-type product policy fees and other revenues	14,002	14,128	13,109
Annuities
Segment Reporting Information [Line Items]
Total premiums, universal life and investment-type product policy fees and other revenues	6,999	5,552	5,730
Property & casualty insurance
Segment Reporting Information [Line Items]
Total premiums, universal life and investment-type product policy fees and other revenues	3,613	3,560	3,504
Non-insurance
Segment Reporting Information [Line Items]
Total premiums, universal life and investment-type product policy fees and other revenues	$ 899	$ 694	$ 710