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Summary of Significant Accounting Policies - Estimated Useful Lives of Assets (Detail)	12 Months Ended
	Apr. 30, 2013
Minimum [Member] | Buildings [Member]
Depreciation Amortization Impairment [Line Items]
Property plant and equipment, estimated useful life	25 years
Minimum [Member] | Machinery and equipment [Member]
Depreciation Amortization Impairment [Line Items]
Property plant and equipment, estimated useful life	5 years
Minimum [Member] | Rolling stock [Member]
Depreciation Amortization Impairment [Line Items]
Property plant and equipment, estimated useful life	5 years
Minimum [Member] | Containers [Member]
Depreciation Amortization Impairment [Line Items]
Property plant and equipment, estimated useful life	5 years
Minimum [Member] | Furniture and Fixtures [Member]
Depreciation Amortization Impairment [Line Items]
Property plant and equipment, estimated useful life	3 years
Maximum [Member] | Buildings [Member]
Depreciation Amortization Impairment [Line Items]
Property plant and equipment, estimated useful life	30 years
Maximum [Member] | Machinery and equipment [Member]
Depreciation Amortization Impairment [Line Items]
Property plant and equipment, estimated useful life	10 years
Maximum [Member] | Rolling stock [Member]
Depreciation Amortization Impairment [Line Items]
Property plant and equipment, estimated useful life	10 years
Maximum [Member] | Containers [Member]
Depreciation Amortization Impairment [Line Items]
Property plant and equipment, estimated useful life	12 years
Maximum [Member] | Furniture and Fixtures [Member]
Depreciation Amortization Impairment [Line Items]
Property plant and equipment, estimated useful life	8 years

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- Details

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- Definition

Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

+ References

No definition available.

+ Details

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