Supplementary Information For Oil And Gas Producing Activities (Standardized Measure Of Discounted Future Net Cash Flows Relating To Proved Oil And Gas Reserves) (Details) (USD $) In Thousands	12 Months Ended
Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2009
Supplementary Information For Oil And Gas Producing Activities [Abstract]
Future Cash Inflows	$ 7,180,320	$ 5,273,605	$ 3,972,026
Future Production Costs	1,555,603	1,347,855	1,010,851
Future Development Costs	636,745	445,413	312,717
Future Income Tax Expense at Applicable Statutory Rate	1,834,778	1,186,567	916,466
Future Net Cash Flows	3,153,194	2,293,770	1,731,992
10% Annual Discount for Estimated Timing of Cash Flows	1,629,037	1,120,182	856,015
Standardized Measure of Discounted Future Net Cash Flows	$ 1,524,157	$ 1,173,588	$ 875,977

Supplementary Information for Oil and Gas Producing Activities (unaudited) [Abstract]

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- Definition

This is the amount that is derived from using a discount rate of ten percent a year to reflect the timing of the future net cash flows relating to proved oil and gas reserves.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 19

-Paragraph 59Y

-Subparagraph e

+ Details

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- Definition

Cash proceeds expected from future sale of oil and gas from proved reserves located in this geographic region. These shall be computed by applying year-end prices of oil and gas relating to the enterprise's proved reserves to the year-end quantities of those reserves. Future price changes shall be considered only to the extent provided by contractual arrangements in existence at year-end.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 19

-Paragraph 59Y

-Subparagraph a

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- Definition

The future cost of developing oil and gas from proved reserves located in this geographic region. These costs are computed by estimating the expenditures to be incurred in developing the proved oil and gas reserves at the end of the year, based on year-end costs and assuming continuation of existing economic conditions.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 19

-Paragraph 59Y

-Subparagraph b

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- Definition

The estimated future income tax expenses that will be incurred based on the future income less future expenses derived from production and sale of proved oil and gas reserves in this geographic region. These expenses are computed by applying the appropriate year-end statutory tax rates, with consideration of future tax rates already legislated, to the future pretax net cash flows relating to the enterprise's proved oil and gas reserves, less the tax basis of the properties involved. The future income tax expenses give effect to tax deductions and tax credits and allowances relating to the enterprise's proved oil and gas reserves

+ References

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 19

-Paragraph 59Y

-Subparagraph c

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- Definition

These amounts are the result of subtracting future development and production costs and future income tax expenses from future cash inflows for each geographic region where proved oil and gas reserves exist.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 19

-Paragraph 59Y

-Subparagraph d

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- Definition

The future cost of producing oil and gas from proved reserves located in this geographic region. These costs are computed by estimating the expenditures to be incurred in producing the proved oil and gas reserves at the end of the year, based on year-end costs and assuming continuation of existing economic conditions.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 19

-Paragraph 59Y

-Subparagraph b

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- Definition

This amount is the future net cash flows less the computed discount.

+ References

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 19

-Paragraph 59Y

-Subparagraph f

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