Long Term Debt (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2011
Debt Instrument
Total debt	$ 1,098,788	$ 1,060,084	$ 1,045,485
Less current maturities	(6,671)	(7,182)	(7,150)
Long-term debt	1,092,117	1,052,902	1,038,335
6.6% Senior Notes, Due 2018
Debt Instrument
Total debt	298,626	298,476	298,428
7% Debentures, Due 2025
Debt Instrument
Total debt	124,437	124,417	124,411
6.25% Senior Notes, Due 2037
Debt Instrument
Total debt	228,105	247,915	247,906
Term Loan Facility, Due 2015
Debt Instrument
Total debt	245,000	250,000	250,000
Revolving Facility
Debt Instrument
Credit Facility	100,000	35,000	20,000
AR Credit Facility
Debt Instrument
Credit Facility	100,000	100,000	100,000
Other notes
Debt Instrument
Other notes	$ 2,620	$ 4,276	$ 4,740

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Amount borrowed under the credit facility as of the balance sheet date.

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Carrying amount of long-term debt, net of unamortized discount or premium, including current and noncurrent amounts. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Carrying amount of long-term debt, net of unamortized discount or premium, scheduled to be repaid within one year or the normal operating cycle, if longer. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Carrying amount of long-term debt, net of unamortized discount or premium, excluding amounts to be repaid within one year or the normal operating cycle, if longer (current maturities). Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Including both current and noncurrent portions, carrying amount as of the balance sheet date of other forms of debt not elsewhere specified in the taxonomy with initial maturities beyond one year or beyond the normal operating cycle, if longer.

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