Debt (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Sep. 30, 2011
Long-term Debt
Carrying value long-term debt	$ 600,000	$ 640,000
Less: current maturities	(133,000)	(40,000)
Total long-term debt due after one year	467,000	600,000
6.375%, due September 2013 [Member] \| Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	6.375%
Long-term Debt
Carrying value long-term debt	108,000	108,000
5.75%, due September 2016 [Member] \| Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.75%
Long-term Debt
Carrying value long-term debt	175,000	175,000
6.21%, due September 2036 [Member] \| Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	6.21%
Long-term Debt
Carrying value long-term debt	100,000	100,000
5.53%, due September 2012 [Member] \| Medium-term Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.53%
Long-term Debt
Carrying value long-term debt	0	40,000
5.37%, due August 2013 [Member] \| Medium-term Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.37%
Long-term Debt
Carrying value long-term debt	25,000	25,000
5.16%, due May 2015 [Member] \| Medium-term Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.16%
Long-term Debt
Carrying value long-term debt	20,000	20,000
7.37%, due October 2015 [Member] \| Medium-term Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	7.37%
Long-term Debt
Carrying value long-term debt	22,000	22,000
5.64%, due December 2015 [Member] \| Medium-term Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.64%
Long-term Debt
Carrying value long-term debt	50,000	50,000
6.17%, due June 2017 [Member] \| Medium-term Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	6.17%
Long-term Debt
Carrying value long-term debt	20,000	20,000
7.25%, due November 2017 [Member] \| Medium-term Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	7.25%
Long-term Debt
Carrying value long-term debt	20,000	20,000
5.67%, due January 2018 [Member] \| Medium-term Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.67%
Long-term Debt
Carrying value long-term debt	20,000	20,000
6.50%, due August 2033 [Member] \| Medium-term Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	6.50%
Long-term Debt
Carrying value long-term debt	20,000	20,000
6.13%, due October 2034 [Member] \| Medium-term Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	6.13%
Long-term Debt
Carrying value long-term debt	$ 20,000	$ 20,000

Interest rate stated in the contractual debt agreement.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

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-Section S99

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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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

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-Subparagraph (SX 210.9-03.16)

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Reference 2: http://www.xbrl.org/2003/role/presentationRef

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Reference 3: http://www.xbrl.org/2003/role/presentationRef

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Reference 4: http://www.xbrl.org/2003/role/presentationRef

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Reference 5: http://www.xbrl.org/2003/role/presentationRef

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Sum of the carrying values as of the balance sheet date of all long-term debt, which is debt initially having maturities due after one year from the balance sheet date or beyond the operating cycle, if longer, but excluding the portions thereof scheduled to be repaid within one year or the normal operating cycle, if longer plus capital lease obligations due to be paid more than one year after the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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Reference 2: http://www.xbrl.org/2003/role/presentationRef

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