Stock Based Awards and Other Equity Instruments -Summary of Unrecognized Stock-Based Compensation Expense and Weighted Average Period Remaining (Details) $ in Millions	6 Months Ended
Jun. 30, 2019 USD ($)
Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation expense	$ 41
Weighted average period remaining (in years)	2 years 10 months 24 days
RSUs/MSUs
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted average period remaining (in years)	2 years 9 months 18 days
Unrecognized compensation expense	$ 292

Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (i)
-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901

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