Earnings Per Share (Computation Of Basic And Diluted Earnings Per Share) (Detail) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Basic earnings per share:
Net income (loss) available to common shareholders	$ (359)	$ (296)	$ (1,605)
Basic weighted average shares	81,014,285	89,013,711	118,930,282
Net income (loss) per basic common share	$ (4.43)	$ (3.33)	$ (13.50)
Diluted earnings per share:
Net income (loss) available to common shareholders	$ (359)	$ (296)	$ (1,605)
Diluted weighted average shares	81,014,285	89,013,711	118,930,282
Net income (loss) per diluted common share	$ (4.43)	$ (3.33)	$ (13.50)
Potentially dilutive securities excluded from the diluted EPS because of antidilutive affect	4,300,000	4,400,000	14,100,000