Share-Based Payments - Stock Option Activities (Details) - Stock Option Plan - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Stock option activity, shares
Stock options at the beginning of the period (in shares)	17,137
Stock options, granted (in shares)	3,992
Stock options, exercised (in shares)	(3,847)
Stock options, forfeited (in shares)	(2,852)
Stock options, expired (in shares)	(401)
Stock options at the ending of the period (in shares)	14,029	17,137
Stock options, vested and expected to vest (in shares)	13,360
Stock options, exercisable (in shares)	5,988
Weighted-average exercise price
Stock options, weighted-average strike price at the beginning of the period (in dollars per share)	$ 39.73
Stock options, weighted-average exercise price, granted (in dollars per share)	49.14
Stock options, weighted-average exercise price, exercised (in dollars per share)	27.31
Stock options, weighted-average exercise price, forfeited (in dollars per share)	46.19
Stock options, weighted-average exercise price, expired (in dollars per share)	46.63
Stock options, weighted-average strike price at the end of the period (in dollars per share)	44.31	$ 39.73
Stock options, weighted-average exercise price, vested and expected to vest (in dollars per share)	43.90
Stock options, weighted-average exercise price, exercisable (in dollars per share)	$ 34.32
Stock options, weighted-average remaining contractual term	7 years 5 months 19 days
Stock options, weighted-average remaining contractual term, vested and expected to vest	7 years 4 months 20 days
Stock options, weighted-average remaining contractual term, exercisable	5 years 6 months 21 days
Stock options, aggregate intrinsic value	$ 221
Stock options, aggregate intrinsic value, vested and expected to vest	216
Stock options, aggregate intrinsic value, exercisable	152
Stock options, intrinsic value of options exercised	80	$ 196	$ 372
Total grant date fair value of options vested	94	$ 45	$ 47
Share-based compensation, unrecognized compensation	$ 78
Share-based compensation, unrecognized compensation weighted-average period of recognition	1 year 3 months 29 days