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, 2019		Dec. 31, 2018	Dec. 31, 2017
RSUs outstanding
Unvested outstanding, Beginning balance		6,640,000		5,802,000	2,856,000
Unvested RSUs, Granted		4,688,000	[1]	3,302,000	4,829,000	[2],[3]
Unvested RSUs, Vested and released	[4]	(2,002,000)		(1,617,000)	(1,030,000)
Unvested RSUs, Cancelled		(857,000)		(847,000)	(853,000)
Unvested outstanding, Ending balance		8,469,000	[5]	6,640,000	5,802,000
Weighted Average Grant-Date Fair Value Per Share
Unvested outstanding, Weighted Average Grant-Date Fair Value Per Share, Beginning balance		$ 44.93		$ 48.81	$ 69.35
Weighted Average Grant-Date Fair Value Per Share, Granted		47.35	[1]	43.04	41.58	[2],[3]
Weighted Average Grant-Date Fair Value Per Share, Vested and released	[4]	48.11		54.22	67.25
Weighted Average Grant-Date Fair Value Per Share, Cancelled		47.19		46.43	52.64
Unvested outstanding, Weighted Average Grant-Date Fair Value Per Share, Ending balance		$ 45.42	[5]	$ 44.93	$ 48.81
Aggregate Intrinsic Value
Unvested RSUs outstanding, Aggregate Intrinsic Value	[5]	$ 258

[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 upon vesting of, the underlying awards.

[2] 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, of which 60,582 RSUs vested and settled during the year ending December 31, 2019 related to the achievement of 2018 annual performance targets. 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.

[3] 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.

[4] Inclusive of 532,164, 424,848, and 301,932 RSUs as of December 31, 2019, 2018 and 2017, 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.

[5] 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.