Consolidated Statement of Comprehensive Income (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Foreign currency translation, Taxes	$ 21	$ (11)	$ (101)
Change in net unrealized losses on available-for-sale securities, Taxes	272	(119)	(195)
Change in net unrealized losses on available-for-sale securities designated in fair value hedges, Taxes	16	16	5
Other-than-temporary impairment on held-to-maturity securities related to factors other than credit, Taxes	3	5	8
Change in net unrealized losses on cash flow hedges, Taxes	(181)	(42)	24
Change in unrealized losses on retirement plans, Taxes	$ 8	$ 1	$ 51