Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Numerator:
Net income attributable to stockholders		$ 5	$ 52	$ 183	$ 418
Earnings allocated to participating securities				(1)	(1)
Net income attributable to stockholders, net of earnings allocated to participating securities		$ 5	$ 52	$ 182	$ 417
Denominator:
Weighted average shares outstanding – basic		206	200	203	204
Unvested restricted shares		1	1	1	1
Weighted average shares outstanding – diluted		207	201	204	205
Basic EPS	[1]	$ 0.02	$ 0.26	$ 0.90	$ 2.04
Diluted EPS	[1]	$ 0.02	$ 0.26	$ 0.90	$ 2.04

[1] Per share amounts are calculated based on unrounded numbers and are calculated independently for each period presented.