Debt - Debt Maturities, Assuming the Exercise of all Extensions that are Exercisable Solely at our Option (Parenthetical) (Detail) $ in Millions	6 Months Ended
	Jun. 30, 2021 USD ($)
Debt Instrument [Line Items]
Outstanding balance, due in 2021	$ 7	[1]
Revolver [Member]
Debt Instrument [Line Items]
Outstanding balance, due in 2021	$ 2
Extension period	2 years

[1] Includes $2 million of the then current outstanding balance under the Revolver; however, we have sufficient capacity with extended undrawn commitments under the Revolver to effectively extend for two years.