Shareholders' Equity - Additional Information (Detail) (USD $)	0 Months Ended			12 Months Ended							1 Months Ended		0 Months Ended
	Dec. 03, 2013	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013 Treasury Stock	Dec. 31, 2012 Treasury Stock	Dec. 31, 2011 Treasury Stock	Dec. 31, 2013 Additional Paid-in Capital	Dec. 31, 2013 Nonvoting Common Stock	Dec. 31, 2012 Nonvoting Common Stock	Dec. 07, 2010 Nonvoting Common Stock	Mar. 31, 2010 Nonvoting Common Stock And Class A Common Stock	Dec. 07, 2010 Nonvoting Common Stock And Class A Common Stock	Feb. 04, 2014 Subsequent Event
Class of Stock [Line Items]
Treasury Shares		17,795,293	15,031,741
Additional authorized shares purchased		11,497,373
Common stock repurchased	3,502,627							3,502,627	1,236,689				1,000,952
Preferred stock, authorized		1,000,000
Common Stock, Par Value		$ 0.50	$ 0.50							$ 0.50
Common Stock, Shares Authorized		225,000,000	225,000,000									225,000,000
Stock split conversion ratio											1.5
Stock Repurchased During Period, Value	$ 125,000,000
Stock Repurchase Program, Percent of Shares Authorized for Repurchase	80.00%
Stock Repurchased and Retired During Period, Value				$ 100,000,000	$ 34,131,000	$ 129,958,000	$ 25,000,000
Accelerated Share Repurchases, Initial Price Paid Per Share				$ 28.55