Common Stock - Additional Information (Detail) $ / shares in Units, $ in Millions		1 Months Ended	3 Months Ended	9 Months Ended
	Oct. 05, 2016 $ / shares shares	Aug. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2016 USD ($)	Oct. 04, 2016 $ / shares shares
Class of Stock [Line Items]
Reverse stock split ratio				0.33
Decrease in common stock due to reverse stock split				$ (877)
Increase in additional paid in capital due to reverse stock split				877
Retirement of treasury stock		$ 76
Common Stock [Member]
Class of Stock [Line Items]
Retirement of treasury stock		(76)	$ 76	76
Additional Capital [Member]
Class of Stock [Line Items]
Retirement of treasury stock		$ (2,563)	$ 2,563	$ 2,563
Subsequent Event [Member]
Class of Stock [Line Items]
Reverse stock split ratio	0.33
Common stock shares outstanding | shares	400,000,000				1,300,000,000
Common stock shares authorized | shares	600,000,000				1,800,000,000
Common stock par value | $ / shares	$ 1.00				$ 1.00