Subsidiary Guarantors - Schedule of Consolidating Statement of Comprehensive Loss (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Oct. 31, 2013	Oct. 31, 2012	Oct. 31, 2013	Oct. 31, 2012
Condensed Financial Statements, Captions [Line Items]
Net income (loss)	$ (575)	$ (21,092)	$ (738)	$ (29,471)
Other comprehensive income (loss), net of taxes:
Unrealized gain (loss) resulting from changes in fair value of derivative instruments, net	(279)	(716)	(568)	(2,799)
Realized loss (gain) on derivative instruments reclassified into earnings, net	181	3,946	345	3,990
Unrealized gain (loss) resulting from changes in fair value of marketable securities	18	21	18	15
Other comprehensive income (loss)	(80)	3,251	(205)	1,206
Comprehensive income (loss)	(655)	(17,841)	(943)	(28,265)
Less: Comprehensive income (loss) attributable to noncontrolling interests	(236)	(125)	(207)	(133)
Comprehensive income (loss )attributable to common stockholders	(419)	(17,716)	(736)	(28,132)
Parent [Member]
Condensed Financial Statements, Captions [Line Items]
Net income (loss)	(339)	(20,967)	(531)	(29,338)
Other comprehensive income (loss), net of taxes:
Unrealized gain (loss) resulting from changes in fair value of derivative instruments, net				(1,257)
Realized loss (gain) on derivative instruments reclassified into earnings, net		3,625		3,625
Other comprehensive income (loss)		3,625		2,368
Comprehensive income (loss)	(339)	(17,342)	(531)	(26,970)
Comprehensive income (loss )attributable to common stockholders	(339)	(17,342)	(531)	(26,970)
Guarantors [Member]
Condensed Financial Statements, Captions [Line Items]
Net income (loss)	10,927	(1,998)	21,070	(3,769)
Other comprehensive income (loss), net of taxes:
Unrealized gain (loss) resulting from changes in fair value of marketable securities	18	21	18	15
Other comprehensive income (loss)	18	21	18	15
Comprehensive income (loss)	10,945	(1,977)	21,088	(3,754)
Comprehensive income (loss )attributable to common stockholders	10,945	(1,977)	21,088	(3,754)
Non-Guarantors [Member]
Condensed Financial Statements, Captions [Line Items]
Net income (loss)	(406)	(402)	(1,349)	(2,205)
Other comprehensive income (loss), net of taxes:
Unrealized gain (loss) resulting from changes in fair value of derivative instruments, net	(279)	(716)	(568)	(1,542)
Realized loss (gain) on derivative instruments reclassified into earnings, net	181	321	345	365
Other comprehensive income (loss)	(98)	(395)	(223)	(1,177)
Comprehensive income (loss)	(504)	(797)	(1,572)	(3,382)
Less: Comprehensive income (loss) attributable to noncontrolling interests	(236)	(125)	(207)	(133)
Comprehensive income (loss )attributable to common stockholders	(268)	(672)	(1,365)	(3,249)
Elimination [Member]
Condensed Financial Statements, Captions [Line Items]
Net income (loss)	(10,757)	2,275	(19,928)	5,841
Other comprehensive income (loss), net of taxes:
Comprehensive income (loss)	(10,757)	2,275	(19,928)	5,841
Comprehensive income (loss )attributable to common stockholders	$ (10,757)	$ 2,275	$ (19,928)	$ 5,841