Net Income Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
NUMERATOR:
Net income	$ 387	$ 463
DENOMINATOR:
Weighted-average shares outstanding, basic	551	587
Dilutive effect of Employee stock options and restricted stock units	1	1
Adjusted weighted-average shares outstanding, diluted	552	588
NET INCOME PER SHARE:
Basic	$ 0.70	$ 0.79
Diluted	$ 0.70	$ 0.79
Restricted Stock Units (RSUs)
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive amounts excluded from calculations	1	0

Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

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