Amount before allocation of valuation allowances of deferred tax asset attributable to deductible capital loss carryforwards.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible operating loss carryforwards.

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- Definition

This element represents the total of accruals as of the date of the statement of financial position for interest recognized for an underpayment of income taxes computed by applying the applicable statutory rate of interest to the difference between a tax position recognized for financial reporting purposes and the amount previously taken or expected to be taken in a tax return of the entity and the amount of statutory penalties for a tax position claimed or expected to be claimed by the entity, in its tax return, that does not meet the minimum statutory threshold to avoid payment of penalties.

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- Definition

This element represents the total of interest expense recognized for an underpayment of income taxes computed by applying the applicable statutory rate of interest to the difference between a tax position recognized for financial reporting purposes and the amount previously taken or expected to be taken in a tax return of the entity and the amount of statutory penalties in the period in which the entity claims or expects to claim a tax position, in its tax return, that does not meet the minimum statutory threshold to avoid payment of penalties.

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Income Taxes - Additional Information (Detail) (USD $)	9 Months Ended
Income Taxes - Additional Information (Detail) (USD $)	Jan. 31, 2013	Apr. 30, 2012	Apr. 30, 2011	Apr. 30, 2010	Apr. 30, 2009
Income Taxes [Line Items]
Capital losses		$ 184,600,000	$ 184,800,000
Non-capital losses		494,600,000	430,600,000
Unrecognized tax benefits, income tax penalties and interest accrued	4,200,000	2,900,000	3,100,000
Unrecognized tax benefits	17,700,000	15,925,000	15,302,000	16,448,000	15,834,000
Unrecognized tax benefits that would impact effective tax rate	10,300,000
Uncertain tax position, identified and recorded	4,000,000
Unrecognized tax benefits, interest and penalties	1,400,000
Other
Income Taxes [Line Items]
Capital losses		184,600,000	184,800,000
Non-capital losses		242,800,000	152,600,000
LUXEMBOURG
Income Taxes [Line Items]
Non-capital losses		$ 251,800,000	$ 278,000,000