Leases - Lease Costs and Other Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Lease cost
Operating lease cost	$ 43	$ 47
Variable lease cost	2	36
Sublease income	(1)	(1)
Total lease cost	44	82
Other information
Operating cash flows used for operating leases	$ 43	$ 47
Weighted-average remaining lease term - operating leases	49 years	50 years
Weighted-average discount rate - operating leases	5.30%	5.30%