Goodwill and Other Intangible Assets - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended						3 Months Ended
	Jul. 31, 2012	Jul. 31, 2011	Jul. 31, 2010	Jul. 31, 2012 Minimum	Jul. 31, 2012 Maximum	Jan. 31, 2012 Market approach	Jan. 31, 2012 Income approach In Process Research And Development Minimum	Jan. 31, 2012 Income approach In Process Research And Development Maximum
Goodwill and Intangible Assets Disclosure [Line Items]
Goodwill	$ 1,849	$ 1,849
Goodwill impairment losses	0	0
Intangible assets, estimated useful lives				6 months	14 years		9 months	21 months
Amortization expense related to acquired intangible assets	$ 3,063	$ 3,088	$ 2,931
Goodwill, discount rate						15.00%