Other Financing Income - Summary of Financing Income (Detail) - USD ($) $ in Thousands	3 Months Ended
	Jul. 31, 2016	Jul. 31, 2015
Other Financing Income (Charges) [Abstract]
Amortization of deferred financing costs	$ (2,132)	$ (1,861)
Net gain on debt extinguishment	0	14,687
Net loss on fair value of foreign currency forward contracts	0	(15,526)
Net gain on fair value of foreign currency embedded derivatives	8,786	13,709
Amortization of guaranteed residual values	(307)	(148)
Interest expense	(92)	(4,382)
Interest income	1,901	5,790
Other	(656)	(2,175)
Other financing income	$ 7,500	$ 10,094