Components of Accumulated Other Comprehensive Loss, Net (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	$ (1,511)
Other comprehensive (loss) income, unrecognized amounts on retirement benefits	64	$ (9)	$ 52
Other comprehensive (loss) income, foreign currency translation adjustment	546	(583)	(680)
Other comprehensive (loss) income, unrealized gains on available-for-sale securities	500	(30)	225
Other comprehensive (loss) income, unrealized gains on cash flow hedges	3	19	(11)
Other comprehensive income (loss)	1,113	(603)	(414)
Ending balance	(398)	(1,511)
Accumulated Other Comprehensive Loss, Net [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance, unrecognized amounts on retirement benefits	(447)	(438)	(490)
Balance, foreign currency translation adjustment	(1,675)	(1,092)	(412)
Beginning balance	585	615	390
Beginning balance	26	7	18
Beginning balance	(1,511)	(908)	(494)
Other comprehensive (loss) income, unrecognized amounts on retirement benefits	64	(9)	52
Other comprehensive (loss) income, foreign currency translation adjustment	546	(583)	(680)
Other comprehensive (loss) income, unrealized gains on available-for-sale securities	500	(30)	225
Other comprehensive (loss) income, unrealized gains on cash flow hedges	3	19	(11)
Other comprehensive income (loss)	1,113	(603)	(414)
Balance, unrecognized amounts on retirement benefits	(383)	(447)	(438)
Balance, foreign currency translation adjustment	(1,129)	(1,675)	(1,092)
Ending balance	1,085	585	615
Ending balance	29	26	7
Ending balance	$ (398)	$ (1,511)	$ (908)