Shareholders' Equity (Summary of Shares Outstanding) (Detail)	12 Months Ended
	Dec. 31, 2016 $ / shares shares	Dec. 31, 2015 $ / shares shares	Dec. 31, 2014 $ / shares shares
Shareholders' Equity Note [Line Items]
Preferred stock without par value (in dollars per share) | $ / shares	$ 10,000,000
Common stock par value (in dollars per share) | $ / shares	$ 1.667
Shares of common stock authorized	1,200,000,000
Per share cash dividends paid (in dollars per share) | $ / shares	$ 1.56	$ 1.41	$ 1.31
Stockholders' Equity Note, Stock Split, Conversion Ratio	2
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance (in shares)	(266,876,009)	(271,964,566)	(277,292,764)
Purchases (in shares)	(10,725,869)	(6,992,772)	(7,626,382)
Issuances (in shares)	1,180,020	1,904,215	2,298,184
Ending balance (in shares)	(257,330,160)	(266,876,009)	(271,964,566)
Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance (in shares)	(581,146,136)	(581,146,136)	(581,146,136)
Ending balance (in shares)	(581,146,136)	(581,146,136)	(581,146,136)
Treasury Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance (in shares)	(314,270,127)	(309,181,570)	(303,853,372)
Purchases (in shares)	(10,725,869)	(6,992,772)	(7,626,382)
Issuances (in shares)	1,180,020	1,904,215	2,298,184
Ending balance (in shares)	(323,815,976)	(314,270,127)	(309,181,570)