Income Taxes - Summary of Income Tax Recovery (Expense) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Jan. 31, 2014	Jan. 31, 2013	Jan. 31, 2014	Jan. 31, 2013
Summary of Income tax recovery (expense)
Income (loss) from continuing operations before income tax	$ (51,185)	$ (18,603)	$ (127,349)	$ (37,949)
Combined Luxembourg statutory income tax rate	0.00%	0.00%	0.00%	0.00%
Income tax recovery (expense) calculated at statutory rate	0	0	0	0
(Increase) decrease in income tax recovery (expense) resulting from:
Rate differences in various jurisdictions	20,408	11,789	52,997	28,745
Change in tax law	(99)	(401)	(704)	(1,158)
Non-deductible items	(30,287)	(10,607)	(61,254)	(26,815)
Other foreign taxes	(3,378)	(9,434)	(10,668)	(15,229)
Non-deductible portion of capital losses	(3,365)	101	(2,775)	166
Non-taxable income	12,620	7,099	32,019	22,154
Adjustments to prior years	(133)	(1,324)	510	(2,030)
Functional currency adjustments	4,345	(2,741)	7,657	1,457
Valuation allowance	(6,783)	(38,524)	(35,281)	(57,338)
Other	(17)	(261)	10	(558)
Income tax expense	$ (6,689)	$ (44,303)	$ (17,489)	$ (50,606)