Commitments and Contingencies - Additional Information (Detail) (USD $)	1 Months Ended	3 Months Ended			3 Months Ended		12 Months Ended
	Mar. 31, 2013 sqft	Apr. 30, 2013	Apr. 30, 2012	Jan. 31, 2013	Apr. 30, 2013 2017 [Member]	Apr. 30, 2013 Indemnification Agreement [Member]	Jan. 31, 2013 Indemnification Agreement [Member]
Commitments And Contingencies [Line Items]
Net rental expenses		$ 1,100,000	$ 1,100,000
Lease agreement rental area in square feet	35,000
Initial lease term	5 years
Lease termination year	2018-04
Monthly basic rent obligation		44,550			65,400
Average monthly basic rent expense		59,800
Total manufacturing purchase commitments		13,100,000		15,100,000
Payments under indemnification obligations						0	0
Liabilities recorded under indemnification obligations						$ 0	$ 0