Subsidiary Guarantors - Schedule of Consolidating Statements of Operations (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Jul. 31, 2013	Jul. 31, 2012
Condensed Financial Statements, Captions [Line Items]
Revenues	$ 128,558	$ 117,638
Operating expenses:
Cost of operations	88,419	81,345
General and administration	15,078	15,190
Depreciation and amortization	15,197	14,709
Expense from divestiture, acquisition and financing costs	20	553
Severance and reorganization costs	107	34
Total operating expenses	118,821	111,831
Operating income (loss)	9,737	5,807
Other expense (income), net:
Interest income	(12)	(8)
Interest expense	9,359	11,692
(Income) loss from equity method investments	977	1,766
Gain on derivative instruments	(654)
Other income	(138)	(130)
Other expense, net	9,532	13,320
Income (loss) from continuing operations before income taxes	205	(7,513)
Provision (benefit) for income taxes	319	650
Income (loss) from continuing operations	(114)	(8,163)
Discontinued operations:
Income (loss) from discontinued operations, net	329	(216)
Loss on disposal of discontinued operations (net of income tax provision of $0 and $0)	(378)
Net income (loss)	(163)	(8,379)
Less: Net income (loss) attributable to noncontrolling interests	28	(8)
Net income (loss) attributable to common stockholders	(191)	(8,371)
Parent [Member]
Operating expenses:
Cost of operations		(6)
General and administration	157	(154)
Depreciation and amortization	214	265
Expense from divestiture, acquisition and financing costs		303
Severance and reorganization costs		34
Total operating expenses	371	442
Operating income (loss)	(371)	(442)
Other expense (income), net:
Interest income	(1)	(8,062)
Interest expense	9,347	11,788
(Income) loss from equity method investments	(9,172)	3,565
Gain on derivative instruments	(654)
Other income	(19)	(12)
Other expense, net	(499)	7,279
Income (loss) from continuing operations before income taxes	128	(7,721)
Provision (benefit) for income taxes	319	650
Income (loss) from continuing operations	(191)	(8,371)
Discontinued operations:
Net income (loss)	(191)	(8,371)
Net income (loss) attributable to common stockholders	(191)	(8,371)
Guarantors [Member]
Condensed Financial Statements, Captions [Line Items]
Revenues	127,693	117,628
Operating expenses:
Cost of operations	87,782	81,342
General and administration	14,927	15,326
Depreciation and amortization	14,802	14,444
Expense from divestiture, acquisition and financing costs	20	250
Severance and reorganization costs	107
Total operating expenses	117,638	111,362
Operating income (loss)	10,055	6,266
Other expense (income), net:
Interest income	(11)	(8)
Interest expense	12	7,966
(Income) loss from equity method investments	(20)	(18)
Other income	(118)	(118)
Other expense, net	(137)	7,822
Income (loss) from continuing operations before income taxes	10,192	(1,556)
Income (loss) from continuing operations	10,192	(1,556)
Discontinued operations:
Income (loss) from discontinued operations, net	329	(216)
Loss on disposal of discontinued operations (net of income tax provision of $0 and $0)	(378)
Net income (loss)	10,143	(1,772)
Net income (loss) attributable to common stockholders	10,143	(1,772)
Non-Guarantors [Member]
Condensed Financial Statements, Captions [Line Items]
Revenues	865	10
Operating expenses:
Cost of operations	637	9
General and administration	(6)	18
Depreciation and amortization	181
Total operating expenses	812	27
Operating income (loss)	53	(17)
Other expense (income), net:
(Income) loss from equity method investments	997	1,784
Other income	(1)
Other expense, net	996	1,784
Income (loss) from continuing operations before income taxes	(943)	(1,801)
Income (loss) from continuing operations	(943)	(1,801)
Discontinued operations:
Net income (loss)	(943)	(1,801)
Less: Net income (loss) attributable to noncontrolling interests	28	(8)
Net income (loss) attributable to common stockholders	(971)	(1,793)
Elimination [Member]
Other expense (income), net:
Interest income		8,062
Interest expense		(8,062)
(Income) loss from equity method investments	9,172	(3,565)
Other expense, net	9,172	(3,565)
Income (loss) from continuing operations before income taxes	(9,172)	3,565
Income (loss) from continuing operations	(9,172)	3,565
Discontinued operations:
Net income (loss)	(9,172)	3,565
Net income (loss) attributable to common stockholders	$ (9,172)	$ 3,565