Earnings Per Share (Computation Of Basic And Diluted Earnings Per Share) (Detail) - USD ($) $ / shares in Units, $ in Millions		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Basic earnings per share:
Net income (loss) available to common shareholders		$ (578)	$ (359)	$ (296)
Basic weighted average shares	[1]	59,071,843	81,014,285	89,013,711
Net income (loss) per basic common share		$ (9.78)	$ (4.43)	$ (3.33)
Diluted earnings per share:
Net income (loss) available to common shareholders		$ (578)	$ (359)	$ (296)
Diluted weighted average shares		59,071,843	81,014,285	89,013,711
Net income (loss) per diluted common share		$ (9.78)	$ (4.43)	$ (3.33)
Potentially dilutive securities excluded from the calculation of diluted EPS because of antidilutive affect		4,600,000	4,300,000	4,400,000

[1] Includes 0.9 million, 1.0 million and 0.8 million of participating securities that met the service condition and were eligible to receive nonforfeitable dividends or dividend equivalents for the years ended December 31, 2020, 2019 and 2018, respectively.