Summary of Accounting Policies - Redeemable Non Controlling Interest (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Redeemable Noncontrolling Interest [Roll Forward]
Beginning Balance	$ 138	$ 42	$ 40
Net income attributable to redeemable noncontrolling interests	27	29	36
Other comprehensive (loss) income		(2)	3
Acquisition and other	17	96	0
Purchase accounting measurement period adjustments	(8)	0	0
Contributions received	0	6	0
Redemption value remeasurement adjustments	58	0	0
Distributions to noncontrolling interests	(26)	(33)	(37)
Ending Balance	$ 196	$ 138	$ 42