Long Term Debt (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014
Debt Instrument [Line Items]
Total debt	$ 1,658,001	$ 1,585,395	$ 1,084,801
Less: Current maturities	(15,966)	(14,336)	(12,404)
Long-term debt	1,642,035	1,571,059	1,072,397
6.6% Senior Notes, Due 2018
Debt Instrument [Line Items]
Total debt	299,243	299,123	299,006
7% Debentures, Due 2025
Debt Instrument [Line Items]
Total debt	124,516	124,500	124,485
6.25% Senior Notes, Due 2037
Debt Instrument [Line Items]
Total debt	228,208	228,184	228,165
4.25% Senior Notes, Due 2024
Debt Instrument [Line Items]
Total debt	395,511	395,309
Floating Rate Notes, Due 2017
Debt Instrument [Line Items]
Total debt	299,108	298,869
Term Loan Facility, Due 2018
Debt Instrument [Line Items]
Total debt	230,167	236,258	242,350
Revolving Facility
Debt Instrument [Line Items]
Total debt			40,000
Trade Receivable Facility
Debt Instrument [Line Items]
Total debt	80,000		150,000
Other Notes
Debt Instrument [Line Items]
Total debt	$ 1,248	$ 3,152	$ 795