Earnings Per Share (Computation Of Basic And Diluted Earnings Per Share) (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Basic earnings per share:
Net income (loss)	$ 71	$ (45)	$ (116)	$ (289)
Less: undistributed earnings allocated to participating securities	4
Net income (loss) available to common shareholders	$ 67	$ (45)	$ (116)	$ (289)
Basic weighted average shares	78,686,542	89,490,267	82,813,523	89,075,892
Net income (loss) per basic common share	$ 0.86	$ (0.50)	$ (1.40)	$ (3.24)
Diluted earnings per share:
Net income (loss)	$ 71	$ (45)	$ (116)	$ (289)
Less: undistributed earnings allocated to participating securities	4
Net income (loss) available to common shareholders	$ 67	$ (45)	$ (116)	$ (289)
Diluted weighted average shares	78,686,542	89,490,267	82,813,523	89,075,892
Net income (loss) per diluted common share	$ 0.86	$ (0.50)	$ (1.40)	$ (3.24)
Potentially dilutive securities excluded from the calculation of diluted EPS because of antidilutive affect	4,500,000	1,400,000	4,500,000	1,400,000