Shareholders' Equity (Additional Information) (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Equity [Abstract]
Preferred stock without par value (in dollars per share)	$ 0
Common stock par value (in dollars per share)	$ 1.667
Shares of common stock authorized	600,000,000
Per share cash dividends paid (in dollars per share)	$ 2.62	$ 2.42	$ 2.34