Summary of Investments (Detail) (USD $) In Thousands, unless otherwise specified	Jan. 31, 2013	Apr. 30, 2012	Apr. 30, 2011
Schedule of Equity and Cost Investments [Line Items]
Equity accounted investments		$ 24,225	$ 23,547
Other, at cost		1	1
Total	25,739	24,226	23,548
TAS
Schedule of Equity and Cost Investments [Line Items]
Percentage ownership		29.90%
Equity accounted investments		15,548	14,250
Luchthaven Den Helder C.V.
Schedule of Equity and Cost Investments [Line Items]
Percentage ownership		50.00%
Equity accounted investments		8,339	9,014
Helideck Certification Agency
Schedule of Equity and Cost Investments [Line Items]
Percentage ownership		50.00%
Equity accounted investments		$ 338	$ 283

This item represents the aggregate carrying amount of all cost-method investments as reported on or included in the balance sheet. The original cost of the investments may differ from the aggregate carrying amount disclosed due to various adjustments such as: (i) dividends received in excess of earnings after the date of investment that are considered a return of investment and therefore recorded as reductions to cost of the investment, or (ii) a series of operating losses of an investee or other factors which may indicate that a decrease in value of the investment has occurred which is other than temporary and accordingly such decrease in value has been recognized.

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

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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.

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

-Publisher FASB

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-Publisher FASB

-Name Emerging Issues Task Force (EITF)

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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.

+ Details

- Definition

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

+ References+ Details