Stock Based Awards and Other Equity Instruments - Summary of RSU Activity (Details) - Restricted Stock Units $ / shares in Units, shares in Thousands, $ in Millions	6 Months Ended
	Jun. 30, 2019 USD ($) $ / shares shares
RSUs outstanding
Unvested outstanding, Beginning balance | shares	6,640
Unvested RSUs, Granted | shares	2,653
Unvested RSUs, Vested and released | shares	(1,755)	[1]
Unvested RSUs, Cancelled | shares	(414)
Unvested outstanding, Ending balance | shares	7,124
Weighted Average Grant-Date Fair Value Per Share
Unvested outstanding, Weighted Average Grant-Date Fair Value Per Share, Beginning balance | $ / shares	$ 44.93
Weighted Average Grant-Date Fair Value Per Share, Granted | $ / shares	53.38
Weighted Average Grant-Date Fair Value Per Share, Vested and released | $ / shares	47.40	[1]
Weighted Average Grant-Date Fair Value Per Share, Cancelled | $ / shares	46.75
Unvested outstanding, Weighted Average Grant-Date Fair Value Per Share, Ending balance | $ / shares	$ 47.70
Aggregate Intrinsic Value
Unvested RSUs outstanding, Aggregate Intrinsic Value | $	$ 332

[1] Inclusive of 461,987 RSUs withheld due to net share settlement to satisfy required employee tax withholding requirements. Potential shares which had been convertible under RSUs that were withheld under net share settlement remain in the authorized but unissued pool under the 2018 Plan and can be reissued by the Company. Total payments for the employees’ tax obligations to the taxing authorities due to net share settlements are reflected as a financing activity within the unaudited condensed consolidated statements of cash flows.