Income Taxes - Reconciliation of Unrecognized Tax Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Unrecognized Tax Benefits [Roll Forward]
Beginning Balance	$ 169	$ 162	$ 115
Additions based on tax positions related to the current year	37	0	113
Additions for tax positions of prior years	25	13	1
Reductions for tax positions for prior years	(18)	(5)	(92)
Acquisition of OpCo	0	0	67
Settlements	0	(1)	0
Effect of changes in federal tax law	0	0	(42)
Ending Balance	$ 213	$ 169	$ 162