Consolidated Statements of Comprehensive Loss (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Oct. 31, 2013	Oct. 31, 2012	Oct. 31, 2013	Oct. 31, 2012
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (575)	$ (21,092)	$ (738)	$ (29,471)
Other comprehensive income (loss), net of taxes:
Unrealized loss resulting from changes in fair value of derivative instruments	(279)	(716)	(568)	(2,799)
Realized loss on derivative instruments reclassified into earnings	181	3,946	345	3,990
Unrealized gain resulting from changes in fair value of marketable securities	18	21	18	15
Other comprehensive (loss) income	(80)	3,251	(205)	1,206
Comprehensive loss	(655)	(17,841)	(943)	(28,265)
Less: Comprehensive loss attributable to noncontrolling interests	(236)	(125)	(207)	(133)
Comprehensive loss attributable to common stockholders	$ (419)	$ (17,716)	$ (736)	$ (28,132)