Share-Based Payments - Stock Option Activities (Details) - Stock Option Plan - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Stock option activity, shares
Stock options at the beginning of the period (in shares)	14,029
Stock options, granted (in shares)	2,419
Stock options, exercised (in shares)	(4,543)
Stock options, forfeited (in shares)	(573)
Stock options, expired (in shares)	(35)
Stock options at the ending of the period (in shares)	11,297	14,029
Stock options, vested and expected to vest (in shares)	10,669
Stock options, exercisable (in shares)	3,710
Weighted-average exercise price per stock option
Stock options, weighted-average strike price at the beginning of the period (in dollars per share)	$ 44.31
Stock options, weighted-average exercise price, granted (in dollars per share)	78.19
Stock options, weighted-average exercise price, exercised (in dollars per share)	37.49
Stock options, weighted-average exercise price, forfeited (in dollars per share)	52.98
Stock options, weighted-average exercise price, expired (in dollars per share)	52.68
Stock options, weighted-average strike price at the end of the period (in dollars per share)	53.84	$ 44.31
Stock options, weighted-average exercise price, vested and expected to vest (in dollars per share)	53.05
Stock options, weighted-average exercise price, exercisable (in dollars per share)	$ 41.56
Stock options, weighted-average remaining contractual term	7 years 8 months 4 days
Stock options, weighted-average remaining contractual term, vested and expected to vest	7 years 7 months 6 days
Stock options, weighted-average remaining contractual term, exercisable	5 years 9 months
Stock options, aggregate intrinsic value	$ 441
Stock options, aggregate intrinsic value, vested and expected to vest	425
Stock options, aggregate intrinsic value, exercisable	190
Stock options, intrinsic value of options exercised	174	$ 80	$ 196
Total grant date fair value of options vested	62	$ 94	$ 45
Share-based compensation, unrecognized compensation	$ 66
Share-based compensation, unrecognized compensation weighted-average period of recognition	1 year 3 months