Capital Stock - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended		31 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Equity [Abstract]
Options and restricted stock, anti-dilutive	4,700,000	10,400,000	6,500,000	8,900,000
Dividends, Common stock	$ 95	$ 95	$ 284	$ 283
Common stock share purchase, shares	40,000,000		40,000,000
Common stock share repurchase, shares					32,200,000
Common stock share repurchase, per share					$ 88.96