Long-Term Debt And Notes Payable (Components Of Debt) (Detail) (USD $)	9 Months Ended
	Sep. 30, 2012		Dec. 31, 2011
Debt Instrument [Line Items]
6.55% notes due 2036	$ 399,048,000		$ 398,914,000
Short-term borrowings	1,114,000		1,112,000
Amended and Restated Credit Agreement term	5 years
Amended and Restated Credit Agreement borrowing capacity	300,000,000
5.50% Notes Due 2013
Debt Instrument [Line Items]
6.55% notes due 2036	199,862,000	[1]	199,753,000	[1]
6.55% Notes Due 2036
Debt Instrument [Line Items]
6.55% notes due 2036	$ 199,186,000		$ 199,161,000

[1] As of September 30, 2012, the Company classified the notes which mature in 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 5-year $300 million Amended and Restated Credit Agreement.