Long-Term Debt (Detail) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015	Jun. 30, 2015
Debt Instrument [Line Items]
Total debt	$ 1,779,217	$ 1,568,774	$ 1,653,338
Less: Current maturities	(238,155)	(18,713)	(15,433)
Long-term debt	1,541,062	1,550,061	1,637,905
6.6% Senior Notes, Due 2018
Debt Instrument [Line Items]
Total debt	299,294	299,113	298,931
7% Debentures, Due 2025
Debt Instrument [Line Items]
Total debt	124,046	124,002	123,960
6.25% Senior Notes, Due 2037
Debt Instrument [Line Items]
Total debt	227,947	227,917	227,898
4.25% Senior Notes, Due 2024
Debt Instrument [Line Items]
Total debt	394,977	394,690	394,441
Floating Rate Notes, Due 2017
Debt Instrument [Line Items]
Total debt	298,793	298,868	298,514
Term Loan Facility, Due 2018
Debt Instrument [Line Items]
Total debt	213,571	222,521	228,346
Trade Receivable Facility
Debt Instrument [Line Items]
Total debt	220,000		80,000
Other Notes
Debt Instrument [Line Items]
Total debt	$ 589	$ 1,663	$ 1,248