Accumulated Other Comprehensive Income (Loss) Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
AOCI Attributable to Parent, Net of Tax [Roll Forward]
AOCI, beginning balance	$ 11,424	$ 10,669
Other Comprehensive Income (Loss), before Tax [Abstract]
Net change, Net of Tax Amount	(2)	37
Cumulative effect of changes in accounting principle	2	121
Other Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax, Portion Attributable to Parent	6	(7)
Other comprehensive income (loss)	40	(6)
AOCI, ending balance	11,136	10,988
Foreign currency translation adjustments: [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
AOCI before tax, beginning balance	(108)	(38)
AOCI tax, beginning balance	5	0
AOCI, beginning balance	(103)	(38)
Other Comprehensive Income (Loss), before Tax [Abstract]
Net change, Before Tax Amount	(3)	41
Net change, Tax Effect	(1)	4
Other Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]
Other comprehensive income (loss)		37
AOCI before tax, ending balance	(111)	3
AOCI tax, ending balance	6	(4)
AOCI, ending balance	(105)	(1)
Unrealized gains (losses) on available-for-sale investment securities: [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
AOCI before tax, beginning balance	(12)	(11)
AOCI tax, beginning balance	4	4
AOCI, beginning balance	(8)	(7)
Other Comprehensive Income (Loss), before Tax [Abstract]
Net change, Before Tax Amount	9	(8)
Net change, Tax Effect	3	0
Other Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]
OCI, before reclassifications, before tax	9	(9)
Other comprehensive income (loss) before reclassifications, tax	(3)	1
OCI, before reclassifications, net of tax	6	(8)
Reclassification from AOCI, current period, before tax	0	1
Reclassification from AOCI, current period, tax	0	0
Reclassification from AOCI, current period, net of tax	0	1
Other comprehensive income (loss)	6	(8)
AOCI before tax, ending balance	(3)	(19)
AOCI tax, ending balance	1	4
AOCI, ending balance	(2)	(15)
Unrealized gains on cash flow hedges: [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
AOCI before tax, beginning balance	(4)	154
AOCI tax, beginning balance	1	(39)
AOCI, beginning balance	(3)	115
Other Comprehensive Income (Loss), before Tax [Abstract]
Net change, Before Tax Amount	43	(49)
Net change, Tax Effect	7	(13)
Other Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]
OCI, before reclassifications, before tax	39	(14)
Other comprehensive income (loss) before reclassifications, tax	(7)	5
OCI, before reclassifications, net of tax	32	(9)
Other comprehensive income (loss)	36	(36)
AOCI before tax, ending balance	39	105
AOCI tax, ending balance	(6)	(26)
AOCI, ending balance	33	79
Unrealized gains on cash flow hedges: [Member] | Cost of revenues [Member]
Other Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]
Reclassification from AOCI, current period, before tax	3	(30)
Reclassification from AOCI, current period, tax	0	7
Reclassification from AOCI, current period, net of tax	3	(23)
Unrealized gains on cash flow hedges: [Member] | Selling, general and administrative expenses [Member]
Other Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]
Reclassification from AOCI, current period, before tax	1	(5)
Reclassification from AOCI, current period, tax	0	1
Reclassification from AOCI, current period, net of tax	1	(4)
Accumulated other comprehensive income (loss):
AOCI Attributable to Parent, Net of Tax [Roll Forward]
AOCI before tax, beginning balance	(124)	105
AOCI tax, beginning balance	10	(35)
AOCI, beginning balance	(114)	70
Other Comprehensive Income (Loss), before Tax [Abstract]
Net change, Before Tax Amount	49	(16)
Net change, Tax Effect	9	(9)
Cumulative Tax Effect Of New Accounting Principle In Period Of Adoption		1
Cumulative effect of changes in accounting principle		(1)
Other Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]
Other comprehensive income (loss)	40	(7)
AOCI before tax, ending balance	(75)	89
AOCI tax, ending balance	1	(26)
AOCI, ending balance	$ (74)	$ 63