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, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Basic earnings per share:
Net income (loss)		$ (123)	$ (58)	$ (290)	$ (497)
Less: undistributed earnings allocated to participating securities		0	0	0	0
Net income (loss) available to common shareholders		$ (123)	$ (58)	$ (290)	$ (497)
Basic weighted average shares	[1]	49,552,796	52,588,533	49,434,177	62,391,826
Net income (loss) per basic common share		$ (2.49)	$ (1.11)	$ (5.87)	$ (7.97)
Diluted earnings per share:
Net income (loss)		$ (123)	$ (58)	$ (290)	$ (497)
Less: undistributed earnings allocated to participating securities		0	0	0	0
Net income (loss) available to common shareholders		$ (123)	$ (58)	$ (290)	$ (497)
Diluted weighted average shares		49,552,796	52,588,533	49,434,177	62,391,826
Net income (loss) per diluted common share		$ (2.49)	$ (1.11)	$ (5.87)	$ (7.97)
Potentially dilutive securities excluded from the calculation of diluted EPS because of antidilutive affect		4,900,000	4,800,000	4,900,000	4,800,000

[1] Includes 0.9 million and 1.0 million of participating securities that met the service condition and were eligible to receive nonforfeitable dividends or dividend equivalents for the three months ended September 30, 2021 and 2020, respectively. 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 nine months ended September 30, 2021 and 2020.