Background (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
New Accounting Pronouncements or Change in Accounting Principle
Net increase in cash, cash equivalents and restricted cash			$ 5,940	$ 14
Income tax expense	$ 47	$ 97	214	362
Operating income	487	593	1,485	1,928
Total other expense, net	348	344	999	982
Accounting Standards Update 2016-09
New Accounting Pronouncements or Change in Accounting Principle
Income tax expense	$ 0		6
Accounting Standards Update 2016-18 | New accounting pronouncement, early adoption, effect
New Accounting Pronouncements or Change in Accounting Principle
Net increase in cash, cash equivalents and restricted cash			6,000
Net cash provided by financing activities			6,000
Accounting Standards Update 2016-09 | Restatement adjustment
New Accounting Pronouncements or Change in Accounting Principle
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
Operating income		(2)		(11)
Total other expense, net		$ (2)		$ (11)