Stockholders' Equity - Restricted Stock Unit Activity (Details) - Restricted Stock Units - $ / shares shares in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Number of Units
Beginning balance (in shares)	15.2	14.3	15.9
Units granted (in shares)	6.3	8.0	6.7
Units vested (in shares)	(5.4)	(5.8)	(6.6)
Units forfeited (in shares)	(2.1)	(1.3)	(1.7)
Ending balance (in shares)	14.0	15.2	14.3
Weighted Average Grant-Date Fair Value
Beginning Balance (in dollars per share)	$ 2,004	$ 1,458	$ 1,024
Units granted (in dollars per share)	3,348	2,373	1,808
Units vested (in dollars per share)	1,704	1,239	827
Units forfeited (in dollars per share)	2,314	1,642	1,223
Ending Balance (in dollars per share)	$ 2,684	$ 2,004	$ 1,458