Subsidiary Guarantors - Schedule of Consolidating Statement of Comprehensive Income (Loss) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended	6 Months Ended
Oct. 31, 2014	Oct. 31, 2013	Oct. 31, 2014	Oct. 31, 2013
Condensed Financial Statements, Captions [Line Items]
Net income (loss)	$ 361	$ (575)	$ 207	$ (738)
Other comprehensive income (loss), net of tax:
Unrealized gain (loss) resulting from changes in fair value of derivative instruments, net		(279)		(568)
Realized loss (gain) on derivative instruments reclassified into earnings, net		181		345
Unrealized gain (loss) resulting from changes in fair value of marketable securities	(6)	18	6	18
Other comprehensive income (loss)	(6)	(80)	6	(205)
Comprehensive income (loss)	355	(655)	213	(943)
Less: Comprehensive income (loss) attributable to noncontrolling interests	102	(236)	238	(207)
Comprehensive income (loss) attributable to common stockholders	253	(419)	(25)	(736)
Parent [Member]
Condensed Financial Statements, Captions [Line Items]
Net income (loss)	259	(339)	(31)	(531)
Other comprehensive income (loss), net of tax:
Unrealized gain (loss) resulting from changes in fair value of derivative instruments, net
Realized loss (gain) on derivative instruments reclassified into earnings, net
Unrealized gain (loss) resulting from changes in fair value of marketable securities
Other comprehensive income (loss)
Comprehensive income (loss)	259	(339)	(31)	(531)
Less: Comprehensive income (loss) attributable to noncontrolling interests
Comprehensive income (loss) attributable to common stockholders	259	(339)	(31)	(531)
Guarantor [Member]
Condensed Financial Statements, Captions [Line Items]
Net income (loss)	11,004	10,927	20,951	21,070
Other comprehensive income (loss), net of tax:
Unrealized gain (loss) resulting from changes in fair value of derivative instruments, net
Realized loss (gain) on derivative instruments reclassified into earnings, net
Unrealized gain (loss) resulting from changes in fair value of marketable securities	(6)	18	6	18
Other comprehensive income (loss)	(6)	18	6	18
Comprehensive income (loss)	10,998	10,945	20,957	21,088
Less: Comprehensive income (loss) attributable to noncontrolling interests
Comprehensive income (loss) attributable to common stockholders	10,998	10,945	20,957	21,088
Non-Guarantor [Member]
Condensed Financial Statements, Captions [Line Items]
Net income (loss)	209	(406)	485	(1,349)
Other comprehensive income (loss), net of tax:
Unrealized gain (loss) resulting from changes in fair value of derivative instruments, net		(279)		(568)
Realized loss (gain) on derivative instruments reclassified into earnings, net		181		345
Unrealized gain (loss) resulting from changes in fair value of marketable securities
Other comprehensive income (loss)		(98)		(223)
Comprehensive income (loss)	209	(504)	485	(1,572)
Less: Comprehensive income (loss) attributable to noncontrolling interests	102	(236)	238	(207)
Comprehensive income (loss) attributable to common stockholders	107	(268)	247	(1,365)
Elimination [Member]
Condensed Financial Statements, Captions [Line Items]
Net income (loss)	(11,111)	(10,757)	(21,198)	(19,928)
Other comprehensive income (loss), net of tax:
Unrealized gain (loss) resulting from changes in fair value of derivative instruments, net
Realized loss (gain) on derivative instruments reclassified into earnings, net
Unrealized gain (loss) resulting from changes in fair value of marketable securities
Other comprehensive income (loss)
Comprehensive income (loss)	(11,111)	(10,757)	(21,198)	(19,928)
Less: Comprehensive income (loss) attributable to noncontrolling interests
Comprehensive income (loss) attributable to common stockholders	$ (11,111)	$ (10,757)	$ (21,198)	$ (19,928)

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.

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Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income (loss) and other comprehensive income (loss), 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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