Background (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net increase in cash, cash equivalents and restricted cash			$ 6,133	$ 65
Income tax expense	$ 23	$ 121	167	265
Operating income	367	647	998	1,335
Total other expense, net	327	330	651	638
Accounting Standards Update 2016-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Income tax expense	$ (1)		6
Accounting Standards Update 2016-18 | New accounting pronouncement, early adoption, effect
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net increase in cash, cash equivalents and restricted cash			6,000
Net cash provide by (used in) financing activities			6,000
Accounting Standards Update 2016-09 | Restatement adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect on retained earnings, net of tax			3
Cumulative effect on retained earnings, tax			$ 2
Accounting Standards Update 2017-07 | Restatement adjustment | New accounting pronouncement, early adoption, effect
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating income		(3)		(9)
Total other expense, net		$ (3)		$ (9)