Segment Information (Premiums, Fees and Other Revenues by US and Foreign Operations) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Premiums, Fees & Other Revenues	$ 51,222	$ 45,843	$ 44,370
U.S.
Segment Reporting Information [Line Items]
Premiums, Fees & Other Revenues	36,078	30,971	29,166
Japan
Segment Reporting Information [Line Items]
Premiums, Fees & Other Revenues	6,435	6,444	7,089
Other Foreign
Segment Reporting Information [Line Items]
Premiums, Fees & Other Revenues	$ 8,709	$ 8,428	$ 8,115