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, 2020		Dec. 31, 2019		Dec. 31, 2018
RSUs outstanding
Unvested outstanding, Beginning balance		8,469,000		6,640,000		5,802,000
Unvested RSUs, Granted		6,397,000		4,688,000	[1]	3,302,000
Unvested RSUs, Vested and released	[2]	(3,019,000)		(2,002,000)		(1,617,000)
Unvested RSUs, Cancelled		(3,736,000)		(857,000)		(847,000)
Unvested outstanding, Ending balance		8,111,000	[3]	8,469,000		6,640,000
Weighted Average Grant-Date Fair Value Per Share
Unvested outstanding, Weighted Average Grant-Date Fair Value Per Share, Beginning balance		$ 45.42		$ 44.93		$ 48.81
Weighted Average Grant-Date Fair Value Per Share, Granted		24.41		47.35	[1]	43.04
Weighted Average Grant-Date Fair Value Per Share, Vested and released	[2]	43.48		48.11		54.22
Weighted Average Grant-Date Fair Value Per Share, Cancelled		36.26		47.19		46.43
Unvested outstanding, Weighted Average Grant-Date Fair Value Per Share, Ending balance		$ 32.29	[3]	$ 45.42		$ 44.93
Aggregate Intrinsic Value
Unvested RSUs outstanding, Aggregate Intrinsic Value	[3]	$ 233

[1] Inclusive of 843,426 dividend equivalents issued to employees holding non-vested RSU grant awards in conjunction with our special cash dividend declared on November 1, 2019, which will be payable to the holder subject to, and only upon vesting of, the underlying awards.

[2] Inclusive of 844,279, 532,164, and 424,848 RSUs as of December 31, 2020, 2019 and 2018, 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.

[3] 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.