Business Combinations - Schedule of Purchase Price Paid for Acquisitions (Detail) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Oct. 31, 2014	Oct. 31, 2013	Apr. 30, 2014
Business Acquisition [Line Items]
Cash used in acquisitions, net of cash acquired	$ 314	$ 2,822
Other non-cash considerations		245
Contingent consideration and holdbacks	67	1,556
Total	381	4,594
Equipment	99	495
Other liabilities, net		(38)
Intangible assets	251	1,865
Fair value of assets acquired and liabilities assumed	350	2,322
Excess purchase price to be allocated to goodwill	119,170	2,272	119,139
BBI Acquisition [Member]
Business Acquisition [Line Items]
Cash used in acquisitions, net of cash acquired	$ 314	$ 2,793