Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Consolidated Statements of Comprehensive Income Parenthetical [Abstract]
Unrecognized amounts on retirement benefits, tax	$ 1	$ 7	$ (3)	$ 26
Unrealized (losses) gains on available-for-sale securities, tax	284	53	355	89
Unrealized (losses) gains on cash flow hedges, tax	$ 1	$ (3)	$ (3)	$ (1)