Non-controlling Interests - Changes in Ownership (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Transfers from (to) non-controlling interests:
Increase as a result of exchanges of LLC Units	$ 32	$ 6
Total transfers from (to) non-controlling interests	32	(637)
Class A Common Stock
Transfers from (to) non-controlling interests:
Decrease as a result of issuances of Class A common stock	$ 0	$ (643)