Segment Information - Summary of Consolidated Financial Statement by Segment (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	Apr. 30, 2013
Segment Reporting Information [Line Items]
Revenue	$ 453,894		$ 441,839		$ 1,312,197		$ 1,304,694
Direct costs	(321,797)	[1]	(303,482)	[1]	(926,252)	[1]	(903,739)
Earnings from equity accounted investees	2,072		850		5,990		2,687
General and administration costs	(39,182)		(18,729)		(77,839)		(56,299)
Adjusted EBITDAR	94,987	[2]	120,478	[2]	314,096	[2]	347,343
Aircraft lease and associated costs	(56,216)		(52,163)		(166,661)		(149,390)
Depreciation	(35,407)		(28,701)		(106,158)		(84,646)
Restructuring costs	0		(4,890)		0		(8,617)
Asset impairments	58		(7,813)		(22,956)		(24,218)
Loss on disposal of assets	2,478		(4,402)		(1,943)		(9,019)
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 income (charges)	(5,730)		(10,852)		(1,615)		(22,435)
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)
Segment assets	3,167,223				3,167,223
Segment assets - held for sale	32,637				32,637
Total assets	3,199,860				3,199,860			2,893,768
Revenue from external customers
Segment Reporting Information [Line Items]
Revenue	453,894		441,839		1,312,197		1,304,694
Inter-segment revenues
Segment Reporting Information [Line Items]
Revenue	0		0		0		0
Helicopter Services
Segment Reporting Information [Line Items]
Revenue	419,314		413,910		1,216,457		1,211,868
Direct costs	(303,677)	[1]	(293,346)	[1]	(863,171)	[1]	(870,452)
Earnings from equity accounted investees	2,072		850		5,990		2,687
General and administration costs	0		0		0		0
Adjusted EBITDAR	117,709	[2]	121,414	[2]	359,276	[2]	344,103
Aircraft lease and associated costs	(56,216)		(52,163)		(166,661)		(149,390)
Asset impairments					(21,900)		(24,100)
Segment assets	1,906,172				1,906,172
Segment assets - held for sale	32,637				32,637
Total assets	1,938,809				1,938,809
Helicopter Services | Revenue from external customers
Segment Reporting Information [Line Items]
Revenue	417,196		412,370		1,212,561		1,208,191
Helicopter Services | Inter-segment revenues
Segment Reporting Information [Line Items]
Revenue	2,118		1,540		3,896		3,677
Heli-One
Segment Reporting Information [Line Items]
Revenue	105,956		99,907		307,361		313,924
Direct costs	(89,497)	[1]	(81,510)	[1]	(273,315)	[1]	(252,613)
Earnings from equity accounted investees	0		0		0		0
General and administration costs	0		0		0		0
Adjusted EBITDAR	16,459	[2]	18,397	[2]	34,046	[2]	61,311
Aircraft lease and associated costs	0		0		0		0
Segment assets	428,551				428,551
Segment assets - held for sale	0				0
Total assets	428,551				428,551
Heli-One | Revenue from external customers
Segment Reporting Information [Line Items]
Revenue	36,698		29,469		99,636		96,503
Heli-One | Inter-segment revenues
Segment Reporting Information [Line Items]
Revenue	69,258		70,438		207,725		217,421
Corporate and Other
Segment Reporting Information [Line Items]
Revenue	0		0		0		0
Direct costs	0	[1]	0	[1]	0	[1]	0
Earnings from equity accounted investees	0		0		0		0
General and administration costs	(39,182)		(18,729)		(77,839)		(56,299)
Adjusted EBITDAR	(39,182)	[2]	(18,729)	[2]	(77,839)	[2]	(56,299)
Aircraft lease and associated costs	0		0		0		0
Asset impairments					(1,100)		(100)
Segment assets	832,500				832,500
Segment assets - held for sale	0				0
Total assets	832,500				832,500
Corporate and Other | Revenue from external customers
Segment Reporting Information [Line Items]
Revenue	0		0		0		0
Corporate and Other | Inter-segment revenues
Segment Reporting Information [Line Items]
Revenue	0		0		0		0
Inter-segment Eliminations
Segment Reporting Information [Line Items]
Revenue	(71,376)		(71,978)		(211,621)		(221,098)
Direct costs	71,377	[1]	71,374	[1]	210,234	[1]	219,326
Earnings from equity accounted investees	0		0		0		0
General and administration costs	0		0		0		0
Adjusted EBITDAR	1	[2]	(604)	[2]	(1,387)	[2]	(1,772)
Aircraft lease and associated costs	0		0		0		0
Segment assets	0				0
Segment assets - held for sale	0				0
Total assets	0				0
Inter-segment Eliminations | Revenue from external customers
Segment Reporting Information [Line Items]
Revenue	0		0		0		0
Inter-segment Eliminations | Inter-segment revenues
Segment Reporting Information [Line Items]
Revenue	$ (71,376)		$ (71,978)		$ (211,621)		$ (221,098)

[1] Direct costs in the segment information presented excludes aircraft lease and associated costs. In the consolidated statement of operations these costs are combined.

[2] Adjusted EBITDAR is defined as earnings before interest, taxes, depreciation, amortization and aircraft lease and associated costs or total revenue plus earnings from equity accounted investees less direct costs excluding aircraft lease and associated costs and general and administration expenses.