Fair Value Level 4 (Details) - Fair Value Hierarchy - USD ($) $ in Millions	6 Months Ended		12 Months Ended
	Dec. 31, 2019	Jun. 30, 2019	Dec. 31, 2020	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liabilities			$ 1
Derivative notional amount, Interest Rate Swap			300
Long-term debt	$ 1,715		1,710
Unrealized (loss) gain on cash flow hedge	2	$ 0	(18)	$ 0
Interest Rate Derivative Liabilities, at Fair Value			(15)
Interest Rate Derivative Assets, at Fair Value	3
Amount of Loss Reclassified from Accumulated OCI into Income			2
Senior Secured Term Loan - USD due 2026 [Domain]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	$ 708		$ 701