Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Numerator:
Net income attributable to stockholders		$ 216	$ 112	$ 366	$ 2,462
Earnings allocated to participating securities		(1)	(1)	(1)	(6)
Net income attributable to stockholders net of earnings allocated to participating securities		$ 215	$ 111	$ 365	$ 2,456
Denominator:
Weighted average shares outstanding - basic		200	214	205	208
Unvested restricted shares		1	1	1
Net effect of shares issued with respect to E&P Dividend	[1]				6
Weighted average shares outstanding - diluted		201	215	206	214
Basic EPS	[2]	$ 1.07	$ 0.52	$ 1.77	$ 11.79
Diluted EPS	[2]	$ 1.07	$ 0.52	$ 1.77	$ 11.48

[1] Shares issued in connection with the distribution of our C corporation earnings and profits attributable to the period prior to spin-off (“E&P Dividend”).

[2] Per share amounts are calculated based on unrounded numbers and are calculated independently for each period presented, therefore, the sum of the quarterly EPS does not equal the EPS for the six months.