Leases (Narrative) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Leases [Abstract]
Lease expense	$ 57	$ 55
Operating lease, cost	38	37
Variable lease, cost	19	18
Capital lease obligations			$ 62
Operating lease, payments	41	34
Right-of-use asset obtained in exchange for operating lease liability	$ 6	$ 12