Goodwill and Other Intangible Assets - Additional Information (Detail) (USD $)	12 Months Ended
	Aug. 31, 2012	Aug. 31, 2011	Aug. 31, 2010
Goodwill and Intangible Assets Disclosure [Line Items]
Weighted-average amortization period for aggregate net intangible assets	10 years 9 months 18 days
Amortization of intangible	$ 16,825,000	$ 22,051,000	$ 25,934,000
Contractual agreements and customer relationships
Goodwill and Intangible Assets Disclosure [Line Items]
Weighted-average amortization period for aggregate net intangible assets	11 years 2 months 12 days
Contractual agreements and customer relationships | Maximum
Goodwill and Intangible Assets Disclosure [Line Items]
Life of intangible assets	15 years
Intellectual property
Goodwill and Intangible Assets Disclosure [Line Items]
Weighted-average amortization period for aggregate net intangible assets	8 years 8 months 12 days
Intellectual property | Maximum
Goodwill and Intangible Assets Disclosure [Line Items]
Life of intangible assets	9 years
Finite lived trade name
Goodwill and Intangible Assets Disclosure [Line Items]
Weighted-average amortization period for aggregate net intangible assets	2 years
Finite lived trade name | Maximum
Goodwill and Intangible Assets Disclosure [Line Items]
Life of intangible assets	2 years
Telmar Network Technology, Inc.
Goodwill and Intangible Assets Disclosure [Line Items]
Acquired intangible assets	49,900,000
Amount of goodwill	60,900,000
Telmar Network Technology, Inc. | Intellectual property
Goodwill and Intangible Assets Disclosure [Line Items]
Life of intangible assets	9 years
Acquisition of intangible assets	8,600,000
Telmar Network Technology, Inc. | Finite lived trade name
Goodwill and Intangible Assets Disclosure [Line Items]
Life of intangible assets	2 years
Acquisition of intangible assets	2,700,000
Telmar Network Technology, Inc. | Customer Relationships
Goodwill and Intangible Assets Disclosure [Line Items]
Life of intangible assets	15 years
Acquisition of intangible assets	$ 38,600,000