Stock Based Awards and Other Equity Instruments - Summary of RSU Activity (Details) - Restricted Stock Units - USD ($) $ / shares in Units, $ in Millions		12 Months Ended
		Dec. 31, 2018		Dec. 31, 2017		Dec. 31, 2016
RSUs outstanding
Unvested outstanding, Beginning balance		5,802,000		2,856,000		1,750,000
Unvested RSUs, Granted		3,302,689	[1]	4,829,000	[1],[2]	2,016,000
Unvested RSUs, Vested and released	[3]	(1,617,000)		(1,030,000)		(627,000)
Unvested RSUs, Cancelled		(847,000)		(853,000)		(283,000)
Unvested outstanding, Ending balance		6,640,000		5,802,000		2,856,000
RSUs outstanding, Expected to vest	[4]	6,640,000
Weighted Average Grant-Date Fair Value Per Share
Unvested outstanding, Weighted Average Grant-Date Fair Value Per Share, Beginning balance		$ 48.81		$ 69.35		$ 79.02
Weighted Average Grant-Date Fair Value Per Share, Granted		43.04	[1]	41.58	[1],[2]	63.71
Weighted Average Grant-Date Fair Value Per Share, Vested and released	[3]	54.22		67.25		76.02
Weighted Average Grant-Date Fair Value Per Share, Cancelled		46.43		52.64		73.06
Unvested outstanding, Weighted Average Grant-Date Fair Value Per Share, Ending balance		44.93		$ 48.81		$ 69.35
Weighted Average Grant-Date Fair Value Per Share, Expected to vest	[4]	$ 44.93
Aggregate Intrinsic Value
Unvested RSUs outstanding, Aggregate Intrinsic Value		$ 358
RSUs Vested and expected to vest, Aggregate Intrinsic Value	[4]	$ 358

[1] Excludes from the 2017 RSU grants, a performance-based RSU grant for 213,000 shares awarded to our CEO during November 2017. This award provides for vesting based on the extent to which the Company achieves certain financial and/or the CEO achieves certain strategic performance metrics relative to the targets to be established by the Company’s Compensation Committee. One quarter of these RSUs may vest and settle annually based on actual performance relative to the targets established annually for each of the four fiscal years ending December 31, 2018, December 31, 2019, December 31, 2020, and December 31, 2021. The estimated grant-date fair value per RSU will be calculated upon the establishment of annual performance targets and each tranche will be amortized on a straight-line basis over its requisite service period. At any point in time during the vesting period, the award’s expense to date will at least equal the portion of the grant-date fair value that is expected to vest at that date. Based upon actual attainment relative to the target performance metrics, the CEO has the ability to receive up to 125% of the target number originally granted, or to be issued none at all.

[2] Inclusive of 426,000 service-based RSUs awarded to our CEO during November 2017. The service-based RSU award provides for vesting in two equal annual installments on each of August 1, 2021 and August 1, 2022, subject to the CEO’s continuous employment with, or performance of services for, the Company. The estimated grant-date fair value per RSU, based on the quoted price of our common stock on the date of grant, was $34.71. The estimated grant-date fair value of this award will be amortized on a straight-line basis over the requisite service period through August 1, 2022.

[3] Inclusive of 424,848, 301,932, and 173,429 RSUs as of December 31, 2018, 2017 and 2016, respectively, 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 consolidated statements of cash flows.

[4] The Company accounts for forfeitures as they occur, rather than estimate expected forfeitures as allowed under GAAP and therefore do not include a forfeiture rate in our vested and expected to vest calculation unless necessary for a performance condition award.