Capital Stock - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended			6 Months Ended		49 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Mar. 31, 2016	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017
Equity [Abstract]
Options and restricted stock, anti-dilutive	8,500,000	6,300,000		8,600,000	7,400,000
Dividends, common stock	$ 95	$ 95	$ 95	$ 190	$ 189
Common stock, shares authorized for repurchase	40,000,000			40,000,000		40,000,000
Common stock share repurchase, shares						32,200,000
Common stock share repurchase average price (in USD per share)						$ 88.96