Earnings Per Share (Computation Of Basic And Diluted Earnings Per Share) (Detail) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Basic earnings per share:
Net income (loss)		$ (61)	$ (106)	$ (167)	$ (439)
Less: undistributed earnings allocated to participating securities		0	0	0	0
Net income (loss) available to common shareholders		$ (61)	$ (106)	$ (167)	$ (439)
Basic weighted average shares	[1]	49,488,368	62,605,656	49,373,883	67,347,335
Net income (loss) per basic common share		$ (1.23)	$ (1.69)	$ (3.38)	$ (6.51)
Diluted earnings per share:
Net income (loss)		$ (61)	$ (106)	$ (167)	$ (439)
Less: undistributed earnings allocated to participating securities		0	0	0	0
Net income (loss) available to common shareholders		$ (61)	$ (106)	$ (167)	$ (439)
Diluted weighted average shares		49,488,368	62,605,656	49,373,883	67,347,335
Net income (loss) per diluted common share		$ (1.23)	$ (1.69)	$ (3.38)	$ (6.51)
Potentially dilutive securities excluded from the calculation of diluted EPS because of antidilutive affect		4,900,000	4,900,000	4,900,000	4,900,000

[1] Includes 0.9 million of participating securities that met the service condition and were eligible to receive nonforfeitable dividends or dividend equivalents for each of the three months and six months ended June 30, 2021 and 2020, respectively.