Property and Equipment and Capitalized Internal-Use Software Development Costs - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
Apr. 30, 2013	Apr. 30, 2012	Apr. 30, 2011
Property, Plant and Equipment [Line Items]
Depreciation and amortization	$ 2.9	$ 2.1	$ 1.7
Capitalized internal-use software development costs
Property, Plant and Equipment [Line Items]
Capitalized internal-use software development costs, amortization	$ 2.5	$ 1.0	$ 0.6

The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

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The current period expense charged against earnings on long-lived, physical assets not used in production, and which are not intended for resale, to allocate or recognize the cost of such assets over their useful lives; or to record the reduction in book value of an intangible asset over the benefit period of such asset; or to reflect consumption during the period of an asset that is not used in production.

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