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Commitments and Contingencies - Additional Information (Detail) (USD $)	3 Months Ended		12 Months Ended
	Apr. 30, 2015	Apr. 30, 2014	Jan. 31, 2015
Loss Contingencies [Line Items]
Net operating lease expenses	$ 1,900,000us-gaap_OperatingLeasesRentExpenseNet	$ 1,300,000us-gaap_OperatingLeasesRentExpenseNet
Total manufacturing purchase commitments	38,100,000		27,500,000
Indemnification agreement [Member]
Loss Contingencies [Line Items]
Payments under indemnification obligations	0		0
Liabilities recorded under indemnification obligations	$ 0		$ 0

Minimum amount to be expended to satisfy the terms of arrangements in which the entity has agreed to expend funds to procure goods or services, excluding long-term purchase commitments or unconditional purchase obligations.

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