Restructuring Accrual Activity (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jan. 31, 2013	Jan. 31, 2012	Jan. 31, 2013	Jan. 31, 2012
Restructuring Cost and Reserve [Line Items]
Beginning Balance			$ 4,061	$ 4,767
Additions to expense	69	141	300	187
Accretion			107	82
Stock based compensation			(48)
Cash paid			(1,061)	(755)
Ending Balance	3,359	4,281	3,359	4,281
Accrued expenses
Restructuring Cost and Reserve [Line Items]
Restructuring reserve, current	1,183	1,336	1,183	1,336
Other long-term liabilities
Restructuring Cost and Reserve [Line Items]
Restructuring reserve, noncurrent	2,176	2,945	2,176	2,945
Employee Severance
Restructuring Cost and Reserve [Line Items]
Beginning Balance			364	6
Additions to expense			231	107
Accretion
Stock based compensation			(48)
Cash paid			(302)	(6)
Ending Balance	245	107	245	107
Employee Severance | Accrued expenses
Restructuring Cost and Reserve [Line Items]
Restructuring reserve, current	245	107	245	107
Norwood, Massachusetts Facility Lease
Restructuring Cost and Reserve [Line Items]
Beginning Balance			3,697	4,761
Additions to expense			69	80
Accretion			107	82
Stock based compensation
Cash paid			(759)	(749)
Ending Balance	3,114	4,174	3,114	4,174
Norwood, Massachusetts Facility Lease | Accrued expenses
Restructuring Cost and Reserve [Line Items]
Restructuring reserve, current	938	1,229	938	1,229
Norwood, Massachusetts Facility Lease | Other long-term liabilities
Restructuring Cost and Reserve [Line Items]
Restructuring reserve, noncurrent	$ 2,176	$ 2,945	$ 2,176	$ 2,945