Leases (Narrative) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Leases, Operating [Abstract]
Lease expense	$ 55	$ 62	$ 66
Operating lease, cost	37
Variable lease, cost	18
Operating lease, payments	34
Right-of-use asset obtained in exchange for operating lease liability	$ 12