Condensed Combined and Consolidated Debtor-in-Possession Financial Information - Debtors' Combined and Consolidated Statements of Operations (Details) - USD ($) $ in Thousands	3 Months Ended
	Jul. 31, 2016	Jul. 31, 2015
Condensed Income Statements, Captions [Line Items]
Revenue	$ 270,436	$ 375,937
Direct costs	(246,861)	(314,170)
Earnings from equity accounted investees	261	1,433
General and administration costs	(15,428)	(16,356)
Depreciation	(35,698)	(40,281)
Restructuring expense	(2,405)	(19,379)
Loss on disposal of assets	(1,125)	(987)
Operating expenses:	(301,256)	(389,740)
Operating loss	(30,820)	(13,803)
Other financing income	7,500	10,094
Reorganization items, net	(785,390)	0
Loss before income tax	(835,733)	(40,734)
Income tax expense	(59)	(5,908)
Net loss	(835,792)	(46,642)
Controlling interest	(835,349)	(53,362)
Non-controlling interests	(443)	6,720
Comprehensive loss	(821,377)	$ (69,697)
Debtors-in Possession
Condensed Income Statements, Captions [Line Items]
Revenue	173,130
Direct costs	(131,818)
Earnings from equity accounted investees	(4,544)
General and administration costs	(17,340)
Depreciation	(28,713)
Restructuring expense	(602)
Loss on disposal of assets	(1,063)
Operating expenses:	(184,080)
Operating loss	(10,950)
Other financing income	(38,924)
Reorganization items, net	(785,390)
Loss before income tax	(835,264)
Income tax expense	(85)
Net loss	(835,349)
Controlling interest	(835,349)
Non-controlling interests	0
Comprehensive loss	$ (822,052)