Intangible Assets - Components of Intangible Assets (Detail) (USD $) In Thousands, unless otherwise specified	Jul. 31, 2013	Apr. 30, 2013
Finite-Lived Intangible Assets [Line Items]
Intangible assets	$ 28,703	$ 28,703
Less accumulated amortization	(17,551)	(17,029)
Intangible assets	11,152	11,674
Covenants Not to Compete [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible assets	17,043	17,043
Less accumulated amortization	(14,939)	(14,800)
Intangible assets	2,104	2,243
Client Lists [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible assets	11,660	11,660
Less accumulated amortization	(2,612)	(2,229)
Intangible assets	$ 9,048	$ 9,431

Accumulated amount of amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 30

-Section 50

-Paragraph 2

-Subparagraph (a)(1)

-URI http://asc.fasb.org/extlink&oid=26713463&loc=d3e16323-109275

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- Definition

Amount before amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

+ References

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- Definition

Amount after amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

+ References

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