Summary of Significant Accounting Policies - Redeemable Non Controlling Interest (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Redeemable Noncontrolling Interest [Roll Forward]
Balance at beginning of period	$ 78	$ 196
Net income (loss) attributable to redeemable noncontrolling interests	7	(4)
Other comprehensive income (loss)	(3)	(7)
Noncontrolling interest tender offer redemption	0	46
Redemption value measurement adjustment	5	15
Reclassification of noncontrolling interest to permanent equity	0	(82)
Balance at end of period	$ 87	$ 72