Long Term Debt (Detail) (USD $)	Jun. 30, 2014	Dec. 31, 2013	Jun. 30, 2013
Debt Instrument
Total debt	$ 1,084,801,000	$ 1,030,921,000	$ 1,093,319,000
Less: Current maturities	12,404,000	12,403,000	6,169,000
Long-term debt	1,072,397,000	1,018,518,000	1,087,150,000
6.6% Senior Notes, Due 2018
Debt Instrument
Total debt	299,006,000	298,893,000	298,783,000
7% Debentures, Due 2025
Debt Instrument
Total debt	124,485,000	124,471,000	124,457,000
6.25% Senior Notes, Due 2037
Debt Instrument
Total debt	228,165,000	228,148,000	228,130,000
Term Loan Facility, Due 2018
Debt Instrument
Total debt	242,350,000	248,441,000	240,000,000
Trade Receivable Credit Facility
Debt Instrument
Credit Facility	150,000,000	130,000,000	150,000,000
Other notes
Debt Instrument
Other notes	795,000	968,000	1,949,000
Revolving Facility
Debt Instrument
Credit Facility	$ 40,000,000		$ 50,000,000