Stock-Based Compensation - Stock Option Activity under All Plans and Other Grants (Detail) - USD ($) $ / shares in Units, $ in Thousands		6 Months Ended	12 Months Ended
		Sep. 30, 2015	Mar. 31, 2015
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of Shares, Outstanding, Beginning Balance		1,155,999
Number of Shares, Granted		120,000	440,000
Number of Shares, Exercised		(74,500)
Number of Shares, Canceled or expired		(36,000)
Number of Shares, Outstanding, Ending Balance		1,165,499	1,155,999
Number of Shares, Options exercisable at September 30, 2015		753,499
Number of Shares, Unvested options expected to become exercisable after September 30, 2015		412,000
Number of Shares, Shares available for future option grants at September 30, 2015	[1]	169,232
Aggregate Intrinsic Value, Outstanding, Beginning Balance		$ 1,480
Aggregate Intrinsic Value, Exercised		282
Aggregate Intrinsic Value, Outstanding, Ending Balance		4,896	$ 1,480
Aggregate Intrinsic Value, Options exercisable at September 30, 2015		3,585
Aggregate Intrinsic Value, Unvested options expected to become exercisable after September 30, 2015		$ 1,310
Approximate Remaining Contractual Term, Outstanding		8 years	8 years
Approximate Remaining Contractual Term, Granted		10 years
Approximate Remaining Contractual Term, Options exercisable at September 30, 2015		7 years
Approximate Remaining Contractual Term, Unvested options expected to become exercisable after September 30, 2015		9 years
Weighted-Average Exercise Price Outstanding, Beginning Balance		$ 9.26
Weighted-Average Exercise Price, Granted		11.85
Weighted-Average Exercise Price, Exercised		8.62
Weighted-Average Exercise Price, Canceled or expired		8.61
Weighted-Average Exercise Price, Outstanding, Ending Balance		9.78	$ 9.26
Weighted-Average Exercise Price, Options exercisable at September 30, 2015		9.22
Weighted-Average Exercise Price, Unvested options expected to become exercisable after September 30, 2015		$ 10.80

[1] May be decreased by restricted stock grants.