Shareholders' Equity (Summary of Shares Outstanding) (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Shareholders' Equity Note [Line Items]
Common Stock, Par or Stated Value Per Share	$ 1.667
Preferred stock without par value (in dollars per share)	$ 10,000,000
Shares of common stock authorized	1,200,000,000
Per share cash dividends paid (in dollars per share)	$ 1.86	$ 1.70	$ 1.56
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance (in shares)	251,174,399	257,330,160	266,876,009
Purchases (in shares)	(15,877,364)	(7,427,557)	(10,725,869)
Issuances (in shares)	564,399	1,271,796	1,180,020
Ending balance (in shares)	235,861,434	251,174,399	257,330,160
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)	329,971,737	323,815,976	314,270,127
Purchases (in shares)	(15,877,364)	(7,427,557)	(10,725,869)
Issuances (in shares)	564,399	1,271,796	1,180,020
Ending balance (in shares)	345,284,702	329,971,737	323,815,976