Computation of Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Earnings Per Share [Abstract]
Net income (loss) for basic and diluted EPS	$ (684)	$ 302	$ 165
Basic weighted average shares outstanding	70.5	75.2	79.3
Options, warrants and non-vested stock	0.0	0.5	0.8
Diluted weighted average shares outstanding	70.5	75.7	80.1
Earnings (loss) per share:
Basic	$ (9.71)	$ 4.01	$ 2.08
Diluted	$ (9.71)	$ 3.98	$ 2.06