Income Taxes (Income Taxes And Related Effective Tax Rates) (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disclosure Income Taxes Income Taxes And Related Effective Tax Rates [Abstract]
Income (loss) before income taxes	$ 89	$ (45)	$ (137)	$ (287)
Provision (benefit) for income taxes	$ 18	$ 0	$ (21)	$ 2
Effective tax rate	20.20%	0.00%	15.30%	(0.70%)