Commitments and Contingencies - Additional Information (Detail) (USD $)	1 Months Ended	12 Months Ended							1 Months Ended
	Mar. 31, 2011	Jul. 31, 2012	Jul. 31, 2011	Jul. 31, 2010	May 31, 2011	May 31, 2011 Minimum [Member]	May 31, 2011 Maximum [Member]	Dec. 31, 2010 Sales Tax Audit [Member]	Feb. 29, 2012 Excise And Similar Taxes [Member]	May 31, 2011 Excise And Similar Taxes [Member]
Commitment And Contingencies [Line Items]
Purchase commitment of company		$ 1,600,000
Accrued tax audits due		2,600,000			1,500,000
Aggregate assessment of tax, interest and penalties					2,700,000			2,100,000		2,500,000
Tax, interest and penalties payment	1,300,000								900,000
Company's excess liability over assessment						0	2,400,000
Rental expenses under operating lease		4,200,000	4,500,000	4,900,000
Connectivity charges under operating lease		16,400,000	19,000,000	21,800,000
Letter of credit and surety bonds outstanding		17,000,000
Collateral to mortgage repayment		10,100,000
Letter of credit expires by July 31, 2012		1,900,000
Letter of credit expires in May and June 2013		100,000
Letter of credit expires in Aug 2015		2,800,000
Refundable customer deposit		$ 10,524,000	$ 1,467,000