Earnings Per Share (Computation Of Basic And Diluted Earnings Per Share) (Detail) - USD ($) $ / shares in Units, shares in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Earnings Per Share [Abstract]
Net income (loss)	$ (481,000,000)	$ 62,000,000	$ (639,000,000)	$ (29,000,000)
Basic weighted average shares outstanding	69,600	76,000	71,300	75,900
Basic	$ (6.91)	$ 0.81	$ (8.96)	$ (0.39)
Diluted	$ (6.91)	$ 0.81	$ (8.96)	$ (0.39)
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Weighted Average Number of Shares Outstanding, Diluted	69,600	76,400	71,300	75,900
Weighted Average Number Diluted Shares Outstanding Adjustment	0	400	0	0
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		500