Income Taxes (Reconciliation of Unrecognized Tax Benefits Roll Forward) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Balance at January 1	$ 106	$ 98	$ 350
Increases-prior period positions	76	8	0
Decreases-prior period positions	(53)	0	(273)
Increases-current period positions	3	0	21
Balance at December 31	$ 132	$ 106	$ 98