Earnings Per Share (Computation Of Basic And Diluted Earnings Per Share) (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Earnings Per Share [Abstract]
Net income (loss) for basic and diluted EPS	$ 398	$ (481)	$ 228	$ (639)
Basic weighted average shares outstanding (in shares)	69,900	69,600	69,900	71,300
Non-vested stock (in shares)	700	0	700	0
Diluted weighted average shares outstanding (in shares)	70,600	69,600	70,600	71,300
Earnings (loss) per share:
Basic (in dollars per share)	$ 5.69	$ (6.91)	$ 3.26	$ (8.96)
Diluted (in dollars per share)	$ 5.63	$ (6.91)	$ 3.23	$ (8.96)
Non-vested stock awards
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities (in shares)		1,300		1,300