Components of Accumulated Other Comprehensive Loss, Net (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification			$ 0
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance - Accumulated other comprehensive loss, net			(398)
Other comprehensive income (loss), unrecognized amounts on retirement benefits	$ (1)	$ 15	50	$ 16
Other comprehensive income (loss), foreign currency translation adjustment	(2)	227	(236)	535
Unrealized gains on marketable securities, net of tax	0	423	0	542
Other comprehensive income (loss), unrealized gains (losses) on cash flow hedges	1	1	2	(5)
Other comprehensive income (loss)	(2)	666	(184)	1,088
Ending balance - Accumulated other comprehensive loss, net	(1,667)		(1,667)
Accumulated Other Comprehensive (Loss) Income, Net [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification			(1,085)
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance - unrecognized amounts on retirement benefits			(383)	(447)
Beginning balance - foreign currency translation adjustment			(1,129)	(1,675)
Beginning balance - unrealized gains (losses) on available-for-sale securities			1,085	585
Beginning balance - unrealized gains (losses) on cash flow hedges			29	26
Beginning balance - Accumulated other comprehensive loss, net			(398)	(1,511)
Other comprehensive income (loss), unrecognized amounts on retirement benefits			50	16
Other comprehensive income (loss), foreign currency translation adjustment			(236)	535
Unrealized gains on marketable securities, net of tax			0	542
Other comprehensive income (loss), unrealized gains (losses) on cash flow hedges			2	(5)
Other comprehensive income (loss)			(184)	1,088
Ending balance - unrecognized amounts on retirement benefits	(333)	(431)	(333)	(431)
Ending balance - foreign currency translation adjustment	(1,365)	(1,140)	(1,365)	(1,140)
Ending balance - unrealized gains (losses) on available-for-sale securities	0	1,127	0	1,127
Ending balance - unrealized gains (losses) on cash flow hedges	31	21	31	21
Ending balance - Accumulated other comprehensive loss, net	$ (1,667)	$ (423)	$ (1,667)	$ (423)