Stock-Based Awards and Other Equity Instruments - Summary of Stock Option Activity (Details) - Stock Options - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Options
Beginning balance (in shares)	15,653	18,841	17,055
Granted (in shares)	5,342	3,618	5,670
Exercised (in shares)	(2,098)	(3,422)	(2,686)
Cancelled (in shares)	(1,197)	(3,384)	(1,198)
Ending balance (in shares)	17,700	15,653	18,841
Exercisable as of December 31, 2018 (in shares)	7,192
Vested and expected to vest after December 31, 2018 (in shares)	17,700
Weighted Average Exercise Price
Beginning balance (in dollars per share)	$ 95.23	$ 84.07	$ 71.77
Granted (in dollars per share)	104.72	124.08	105.37
Exercised (in dollars per share)	71.36	62.67	47.57
Cancelled (in dollars per share)	107.26	96.86	91.62
Ending balance (in dollars per share)	100.11	$ 95.23	$ 84.07
Exercisable as of December 31, 2018 (in dollars per share)	88.02
Vested and expected to vest after December 31, 2018 (in dollars per share)	$ 100.11
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Remaining Contractual Life (In years), Balance as of December 31, 2018	4 years 3 months 20 days
Remaining Contractual Life (In years), Exercisable as of December 31, 2018	2 years 10 months 29 days
Remaining Contractual Life (In years), Vested and expected to vest after December 31, 2018	4 years 3 months 20 days
Aggregate intrinsic value, Balance as of December 31, 2018	$ 261
Aggregate intrinsic value, Exercisable as of December 31, 2018	185
Aggregate intrinsic value, Vested and expected to vest after December 31, 2018	$ 261