Segment Information (Premiums, Universal Life and Investment-Type Policy Fees and Other Revenues by US and Foreign Operations) (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
U.S.
Segment Reporting Information [Line Items]
Total premiums, universal life and investment-type product policy fees and other revenues	30,971	29,166	29,094
Japan
Segment Reporting Information [Line Items]
Total premiums, universal life and investment-type product policy fees and other revenues	6,444	7,089	6,264
Other Foreign
Segment Reporting Information [Line Items]
Total premiums, universal life and investment-type product policy fees and other revenues	$ 8,428	$ 8,115	$ 8,542