Long-Term Debt (Detail) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015
Debt Instrument [Line Items]
Total debt	$ 1,752,757	$ 1,568,774	$ 1,576,063
Less: Current maturities	(177,430)	(18,713)	(13,873)
Long-term debt	1,575,327	1,550,061	1,562,190
Revolving Facility
Debt Instrument [Line Items]
Total debt	30,000
6.6% Senior Notes, Due 2018
Debt Instrument [Line Items]
Total debt	299,201	299,113	298,842
7% Debentures, Due 2025
Debt Instrument [Line Items]
Total debt	124,024	124,002	123,938
6.25% Senior Notes, Due 2037
Debt Instrument [Line Items]
Total debt	227,933	227,917	227,880
4.25% Senior Notes, Due 2024
Debt Instrument [Line Items]
Total debt	394,843	394,690	394,304
Floating Rate Notes, Due 2017
Debt Instrument [Line Items]
Total debt	298,837	298,868	298,304
Term Loan Facility, Due 2018
Debt Instrument [Line Items]
Total debt	217,109	222,521	231,259
Trade Receivable Facility
Debt Instrument [Line Items]
Total debt	159,925
Other Notes
Debt Instrument [Line Items]
Total debt	$ 885	$ 1,663	$ 1,536