Long-Term Debt And Notes Payable (Components Of Debt) (Detail) (USD $)	6 Months Ended
	Jun. 30, 2013		Dec. 31, 2012
Debt Instrument [Line Items]
6.55% notes due 2036	$ 399,181,000		$ 399,092,000
Short-term borrowings	14,422,000		1,123,000
Amended and Restated Credit Agreement term	5 years
Amended and Restated Credit Agreement borrowing capacity	500,000,000
5.50% Notes Due 2013
Debt Instrument [Line Items]
6.55% notes due 2036	199,970,000	[1]	199,898,000	[1]
6.55% Notes Due 2036
Debt Instrument [Line Items]
6.55% notes due 2036	$ 199,211,000		$ 199,194,000

[1] As of June 30, 2013, the Company classified the notes which mature on September 15, 2013 as long-term debt due to the Company's intent to refinance on a long-term basis and the ability to utilize the existing but unused 5-year $500 million Second Amended and Restated Credit Agreement.