Earnings Per Share (Computation Of Basic And Diluted Earnings Per Share) (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Earnings Per Share [Abstract]
Net income (loss)	$ 26	$ 3	$ (61)	$ (104)
Basic weighted average shares outstanding	80.7	84.0	80.8	84.9
Weighted Average Number Diluted Shares Outstanding Adjustment	0.8	1.2	0.0	0.0
Weighted Average Number of Shares Outstanding, Diluted	81.5	85.2	80.8	84.9
Basic	$ 0.33	$ 0.04	$ (0.75)	$ (1.22)
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount			0.1	0.8
Earnings Per Share, Diluted	$ 0.32	$ 0.04	$ (0.75)	$ (1.22)
Restricted Stock Units (RSUs) [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	0.2	0.7	1.5	1.3