Stockholders' Equity (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Net income (loss)
Net income (loss) attributable to common stockholders	$ (692)	$ 61	$ (1,726)	$ (3,207)
Income (loss) effect of TEUs	(2)	0	(3)	0
Less distributions on participating securities	0	1	0	2
Basic	(694)	60	(1,729)	(3,209)
Income (loss) effect of TEUs	(1)	0	(1)	0
Diluted	$ (695)	$ 60	$ (1,730)	$ (3,209)
Shares
Average number of common shares outstanding—basic	510	508	510	507
Dilutive effect of stock options	0	1	0	0
Average number of common shares outstanding—diluted	510	509	510	507
Excluded due to anti-dilutive effect	11	6	10	11
Net income (loss) per common share
Basic	$ (1.36)	$ 0.12	$ (3.39)	$ (6.32)
Diluted	$ (1.36)	$ 0.12	$ (3.39)	$ (6.32)