Stockholders' Equity - Earnings Per Share Reconciliation Table (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Net income (loss)
Net income (loss) attributable to common stockholders	$ (830)	$ (2,235)	$ (2,556)	$ (5,442)
Income (loss) effect of TEUs	(2)	(3)	(5)	(3)
Less distributions on participating securities	1	1	1	4
Basic	(833)	(2,239)	(2,562)	(5,449)
Income (loss) effect of TEUs	0	0	(1)	0
Diluted	$ (833)	$ (2,239)	$ (2,563)	$ (5,449)
Shares
Average number of common shares outstanding—basic	517	508	512	508
Average number of common shares outstanding—diluted	517	508	512	508
Excluded due to anti-dilutive effect	11	10	11	11
Net income (loss) per common share
Basic	$ (1.61)	$ (4.41)	$ (5.00)	$ (10.73)
Diluted	$ (1.61)	$ (4.41)	$ (5.00)	$ (10.73)