Unrecognized Tax Benefits Reconciliation (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Balance at January 1	$ 8	$ 11
Reduction of unrecognized tax benefits due to expiration of statute of limitations	(3)	(3)
Balance at December 31	$ 5	$ 8