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Asset Impairments and Other Items - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended				12 Months Ended							3 Months Ended	12 Months Ended
	Apr. 30, 2014	Apr. 30, 2013	Apr. 30, 2012	Apr. 30, 2014 Tompkins [Member]	Apr. 30, 2013 BBI Acquisition [Member]	Apr. 30, 2014 Western Region [Member] Cares [Member]	Apr. 30, 2012 New York [Member]	Apr. 30, 2012 Vermont [Member]	Apr. 30, 2014 Maine Energy Facility [Member]	Apr. 30, 2013 Maine Energy Facility [Member]	Apr. 30, 2012 Maine Energy Facility [Member]	Apr. 30, 2012 Maine Energy Facility [Member] Eastern Region [Member]	Apr. 30, 2014 Legal Costs [Member] Tompkins [Member]	Apr. 30, 2013 Legal Costs [Member] BBI Acquisition [Member]	Apr. 30, 2013 Second Lien Notes [Member] BBI Acquisition [Member]
Asset Retirement Obligation [Line Items]
Impairment charge	$ 7,455		$ 40,746			$ 7,455						$ 40,746
Discount rate												3.50%
Development project charge	1,394		131						1,394		131
Deferred project costs	0	1,644
Severance and reorganization charge	586	3,709
Liability associated with severance and reorganization	478	680
Legal costs for the acquisition	144	1,410			1,410					505			144	602	303
Equity method investment membership interest				50.00%
Legal settlement expenses			$ 1,359				$ 359	$ 1,000

X

- Definition

Amount recognized as an operating expense or loss during the period to write-off the deferred costs associated with development projects no longer deemed viable.

+ References

No definition available.

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The write-off of costs associated with a financing initiative that is no longer being pursued, legal costs associated with a divestiture and costs associated with an acquisition.

+ References

No definition available.

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- Definition

The remaining liability associated with severance and reorganization.

+ References

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- Definition

Amount of write-down of assets recognized in the income statement. Includes, but is not limited to, losses from tangible assets, intangible assets and goodwill.

+ References

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

-Publisher FASB

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The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

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Interest rate used to find the present value of an amount to be paid or received in the future as an input to measure fair value. For example, but not limited to, weighted average cost of capital (WACC), cost of capital, cost of equity and cost of debt.

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Amount of gain (loss) recognized in settlement of litigation and insurance claims. Excludes claims within an insurance entity's normal claims settlement process.

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Gross amount of other deferred costs capitalized at the end of the reporting period. Does not include deferred finance costs or deferred acquisition costs of insurance companies.

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Amount of expenses for special or contractual termination benefits provided to current employees involuntarily terminated under a benefit arrangement associated exit or disposal activities pursuant to an authorized plan. Excludes expenses related to one-time termination benefits, a discontinued operation or an asset retirement obligation.

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