Asset Allocation and Target Allocation under Helix Plan (Detail) (Helix Plan)	12 Months Ended
Sep. 30, 2011
Helix Plan
Percentage of Plan Assets
Percentage of Plan Assets, Equity securities	17.00%
Percentage of Plan Assets, Debt securities	67.00%
Percentage of Plan Assets, Other	4.00%
Percentage of Plan Assets, Cash	12.00%
Defined Benefit Plan, Actual Plan Asset Allocations, Total	100.00%
Percentage of Target Allocation at the End of Next Fiscal Year
Percentage of Target Allocation at the End of Next Fiscal Year, Equity securities, Minimum	15.00%
Percentage of Target Allocation at the End of Next Fiscal Year, Equity securities, Maximum	30.00%
Percentage of Target Allocation at the End of Next Fiscal Year, Debt securities, Minimum	50.00%
Percentage of Target Allocation at the End of Next Fiscal Year, Debt securities, Maximum	70.00%
Percentage of Target Allocation at the End of Next Fiscal Year, Other, Minimum	0.00%
Percentage of Target Allocation at the End of Next Fiscal Year, Other, Maximum	10.00%
Percentage of Target Allocation at the End of Next Fiscal Year, Cash, Minimum	0.00%
Percentage of Target Allocation at the End of Next Fiscal Year, Cash, Maximum	20.00%

Defined Benefit Plan, Cash and Cash Equivalents

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The percentage of the fair value of debt securities to the fair value of total plan assets held as of the measurement date.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

-Paragraph 5

-Subparagraph d(1)

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

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The percentage of the fair value of equity securities to the fair value of total plan assets held as of the measurement date.

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The percentage of the fair value of investments other than debt securities, equity securities, and real estate to the fair value of total plan assets held as of the measurement date.

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Target allocation maximum percentage of investments in debt securities to total plan assets presented on a weighted-average basis as of the measurement date of the latest statement of financial position.

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Target allocation minimum percentage of investments in debt securities to total plan assets presented on a weighted-average basis as of the measurement date of the latest statement of financial position.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

-Paragraph 5

-Subparagraph d(2)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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Target allocation maximum percentage of investments in equity securities to total plan assets presented on a weighted-average basis as of the measurement date of the latest statement of financial position.

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Target allocation minimum percentage of investments in equity securities to total plan assets presented on a weighted-average basis as of the measurement date of the latest statement of financial position.

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Target allocation maximum percentage in other than debt securities, equity securities, and real estate to total plan assets presented on a weighted-average basis as of the measurement date of the latest statement of financial position.

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Target allocation minimum percentage in other than debt securities, equity securities, and real estate to total plan assets presented on a weighted-average basis as of the measurement date of the latest statement of financial position.

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The aggregate percentage of the fair value of investments (categorized by debt securities, equity securities, real estate and other plan assets) to the fair value of total plan assets held as of the measurement date.

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