Summary of Income tax recovery (expense) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
Jul. 31, 2012	Jul. 31, 2011	Apr. 30, 2012	Apr. 30, 2011	Apr. 30, 2010
Summary of Income tax recovery (expense)
Loss from continuing operations before income tax	$ (31,301)	$ (6,003)	$ (30,676)	$ (94,983)	$ (65,769)
Combined Luxemburg statutory income tax rate	29.00%	29.00%	29.00%	29.00%	29.00%
Income tax recovery calculated at statutory rate	9,077	1,741	8,896	27,545	19,073
(Increase) decrease in income tax recovery (expense) resulting from:
Rate differences in various jurisdictions	2,200	4,316	33,522	60,930	73,116
Change in tax law	(579)	(200)	(3,558)	493	(1,283)
Non-deductible items	(8,470)	(8,842)	(29,365)	(58,007)	(88,132)
Other foreign taxes	(3,432)	(4,805)	(14,846)	(7,740)	(15,593)
Non-deductible portion of capital losses	183	503	991	(373)	4,301
Non-taxable income	7,266	765	10,292	1,442	3,781
Adjustments to prior years	(39)	370	(3,399)	(2,047)	7,781
Functional currency adjustments	8,034	1,695	4,627	32,163	(13,468)
Valuation allowance	(15,161)	7,027	(55,624)	(19,213)	(24)
Other	(360)	1,277	247	(2,277)	1,151
Income tax recovery (expense)	$ (1,281)	$ 3,847	$ (48,217)	$ 32,916	$ (9,297)

Income Tax Reconciliation Functional Currency Adjustments

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Income Tax Reconciliation Non Deductible Portion Of Capital Losses

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Income Tax Reconciliation Other Foreign Taxes

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A ratio calculated by dividing the reported amount of income tax expense attributable to continuing operations for the period by GAAP-basis pretax income from continuing operations.

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This element represents the income or loss from continuing operations attributable to the economic entity which may also be defined as revenue less expenses from ongoing operations, after income or loss from equity method investments, but before income taxes, extraordinary items, and noncontrolling interest.

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The sum of the current income tax expense or benefit and the deferred income tax expense or benefit pertaining to pretax Income or Loss from continuing operations; income tax expense or benefit may include interest and penalties on tax uncertainties based on the entity's accounting policy.

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The portion of the difference between total income tax expense or benefit as reported in the Income Statement and the expected income tax expense or benefit computed by applying the domestic federal statutory income tax rates to pretax income from continuing operations attributable to changes in the valuation allowance for deferred tax assets in the period.

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The amount of income tax expense or benefit for the period computed by applying the domestic federal statutory tax rates to pretax income from continuing operations.

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The sum of the differences between total income tax expense or benefit as reported in the Income Statement for the period and the expected income tax expense or benefit computed by applying the domestic federal statutory income tax rates to pretax income from continuing operations attributable to nondeductible expenses under enacted tax laws, or differences in the methodologies used to determine expense amounts for financial statements prepared in accordance with generally accepted accounting principles and enacted tax laws.

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The portion of the difference, between total income tax expense or benefit as reported in the Income Statement for the year/accounting period and the expected income tax expense or benefit computed by applying the domestic federal statutory income tax rates to pretax income from continuing operations, that is attributable to all other items not otherwise listed in the existing taxonomy.

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The portion of the difference between total income tax expense or benefit as reported in the Income Statement for the current period and the expected income tax expense or benefit computed attributable to revisions of previously reported income tax expense.

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The portion of the difference between total income tax expense or benefit as reported in the Income Statement for the period and the expected income tax expense or benefit computed by applying the domestic federal statutory income tax rates to pretax income from continuing operations attributable to income that is exempt from income taxes under enacted tax laws.

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