Consolidated Statements of Operations (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Jan. 31, 2014	Jan. 31, 2013	Jan. 31, 2014	Jan. 31, 2013
Income Statement [Abstract]
Revenue	$ 453,894	$ 441,839	$ 1,312,197	$ 1,304,694
Operating expenses:
Direct costs	(378,013)	(355,645)	(1,092,913)	(1,053,129)
Earnings from equity accounted investees	2,072	850	5,990	2,687
General and administration costs	(39,182)	(18,729)	(77,839)	(56,299)
Depreciation	(35,407)	(28,701)	(106,158)	(84,646)
Restructuring costs	0	(4,890)	0	(8,617)
Asset impairments (notes 3, 4, 6 and 7)	58	(7,813)	(22,956)	(24,218)
Gain (loss) on disposal of assets	2,478	(4,402)	(1,943)	(9,019)
Operating Expenses	(447,994)	(419,330)	(1,295,819)	(1,233,241)
Operating income	5,900	22,509	16,378	71,453
Interest on long-term debt	(39,782)	(33,991)	(117,636)	(93,949)
Foreign exchange gain (loss)	(11,573)	3,731	(24,476)	6,982
Other financing charges (note 10)	(5,730)	(10,852)	(1,615)	(22,435)
Loss from continuing operations before income tax	(51,185)	(18,603)	(127,349)	(37,949)
Income tax expense (note 12)	(6,689)	(44,303)	(17,489)	(50,606)
Loss from continuing operations	(57,874)	(62,906)	(144,838)	(88,555)
Earnings from discontinued operations, net of tax	0	212	0	1,024
Net loss	(57,874)	(62,694)	(144,838)	(87,531)
Net earnings (loss) attributable to:
Controlling interest	(60,003)	(58,421)	(149,324)	(84,606)
Non-controlling interest	2,129	(4,273)	4,486	(2,925)
Net loss	$ (57,874)	$ (62,694)	$ (144,838)	$ (87,531)
Net loss per ordinary share attributable to controlling interest - basic and diluted (note 11):
Continuing operations (in dollars per share)	$ (1.16)	$ (1.26)	$ (3.10)	$ (1.84)
Discontinued operations (in dollars per share)	$ 0.00	$ 0.00	$ 0.00	$ 0.02
Net loss per ordinary share (in dollars per share)	$ (1.16)	$ (1.26)	$ (3.10)	$ (1.82)
Weighted average number of shares outstanding - basic and diluted:	51,573,832	46,519,484	48,204,267	46,519,484