Subsidiary Guarantors - Schedule of Consolidating Statement of Comprehensive Income (Loss) (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Apr. 30, 2014	Apr. 30, 2013	Apr. 30, 2012
Condensed Financial Statements, Captions [Line Items]
Net loss	$ (27,404)	$ (54,463)	$ (77,592)
Other comprehensive income (loss), net of taxes:
Unrealized loss resulting from changes in fair value of derivative instruments	(36)	(2,910)	(1,749)
Realized loss (gain) on derivative instruments reclassified into earnings	655	4,247	(578)
Unrealized gain (loss) resulting from changes in fair value of marketable securities	12	23	(3)
Other comprehensive income (loss)	631	1,360	(2,330)
Comprehensive loss	(26,773)	(53,103)	(79,922)
Less: Comprehensive loss attributable to noncontrolling interests	(4,309)	(321)	(6)
Comprehensive loss attributable to common stockholders	(22,464)	(52,782)	(79,916)
Parent [Member]
Condensed Financial Statements, Captions [Line Items]
Net loss	(23,095)	(54,142)	(77,586)
Other comprehensive income (loss), net of taxes:
Unrealized loss resulting from changes in fair value of derivative instruments		(1,257)	(2,253)
Realized loss (gain) on derivative instruments reclassified into earnings		3,626	(77)
Unrealized gain (loss) resulting from changes in fair value of marketable securities
Other comprehensive income (loss)		2,369	(2,330)
Comprehensive loss	(23,095)	(51,773)	(79,916)
Less: Comprehensive loss attributable to noncontrolling interests
Comprehensive loss attributable to common stockholders	(23,095)	(51,773)	(79,916)
Guarantors [Member]
Condensed Financial Statements, Captions [Line Items]
Net loss	23,807	(19,954)	(46,144)
Other comprehensive income (loss), net of taxes:
Unrealized loss resulting from changes in fair value of derivative instruments
Realized loss (gain) on derivative instruments reclassified into earnings
Unrealized gain (loss) resulting from changes in fair value of marketable securities	12	23	(3)
Other comprehensive income (loss)	12	23	(3)
Comprehensive loss	23,819	(19,931)	(46,147)
Less: Comprehensive loss attributable to noncontrolling interests
Comprehensive loss attributable to common stockholders	23,819	(19,931)	(46,147)
Non-Guarantors [Member]
Condensed Financial Statements, Captions [Line Items]
Net loss	(9,305)	(5,090)	(20,694)
Other comprehensive income (loss), net of taxes:
Unrealized loss resulting from changes in fair value of derivative instruments	(36)	(1,653)	504
Realized loss (gain) on derivative instruments reclassified into earnings	655	621	(501)
Unrealized gain (loss) resulting from changes in fair value of marketable securities
Other comprehensive income (loss)	619	(1,032)	3
Comprehensive loss	(8,686)	(6,122)	(20,691)
Less: Comprehensive loss attributable to noncontrolling interests	(4,309)	(321)	(6)
Comprehensive loss attributable to common stockholders	(4,377)	(5,801)	(20,685)
Elimination [Member]
Condensed Financial Statements, Captions [Line Items]
Net loss	(18,811)	24,723	66,832
Other comprehensive income (loss), net of taxes:
Unrealized loss resulting from changes in fair value of derivative instruments
Realized loss (gain) on derivative instruments reclassified into earnings
Unrealized gain (loss) resulting from changes in fair value of marketable securities
Other comprehensive income (loss)
Comprehensive loss	(18,811)	24,723	66,832
Less: Comprehensive loss attributable to noncontrolling interests
Comprehensive loss attributable to common stockholders	$ (18,811)	$ 24,723	$ 66,832

Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income, attributable to parent entity. Excludes changes in equity resulting from investments by owners and distributions to owners.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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-Name Accounting Standards Codification

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Amount after tax of (increase) decrease in equity from transactions and other events and circumstances from net income and other comprehensive income, attributable to noncontrolling interests. Excludes changes in equity resulting from investments by owners and distributions to owners.

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Amount after tax and reclassification adjustments, of appreciation (loss) in value of unsold available-for-sale securities. Excludes amounts related to other than temporary impairment (OTTI) loss.

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Amount after tax and reclassification adjustments, of increase (decrease) in accumulated gain (loss) from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's increase (decrease) in deferred hedging gain (loss).

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Amount after tax and reclassification adjustments of other comprehensive income (loss).

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The consolidated profit or loss for the period, net of income taxes, including the portion attributable to the noncontrolling interest.

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