Allocation of Purchase Price for Acquisitions and Enterprise Value of Channel Intelligence (Parenthetical) (Detail)	9 Months Ended	12 Months Ended
	Sep. 30, 2013	Dec. 31, 2012
Technology
Schedule Of Business Acquisitions Purchase Price Allocation [Line Items]
Finite intangible assets, useful life		10 years
Technology | Minimum
Schedule Of Business Acquisitions Purchase Price Allocation [Line Items]
Finite intangible assets, useful life	5 years	5 years
Technology | Maximum
Schedule Of Business Acquisitions Purchase Price Allocation [Line Items]
Finite intangible assets, useful life	10 years	10 years
Non-compete Agreements | Minimum
Schedule Of Business Acquisitions Purchase Price Allocation [Line Items]
Finite intangible assets, useful life	2 years	2 years
Non-compete Agreements | Maximum
Schedule Of Business Acquisitions Purchase Price Allocation [Line Items]
Finite intangible assets, useful life	3 years	3 years
Msdsonline One | Customer Lists | Minimum
Schedule Of Business Acquisitions Purchase Price Allocation [Line Items]
Finite intangible assets, useful life	5 years
Msdsonline One | Customer Lists | Maximum
Schedule Of Business Acquisitions Purchase Price Allocation [Line Items]
Finite intangible assets, useful life	11 years
Msdsonline One | Technology
Schedule Of Business Acquisitions Purchase Price Allocation [Line Items]
Finite intangible assets, useful life	5 years
Msdsonline One | Trademarks, trade names and domain names | Minimum
Schedule Of Business Acquisitions Purchase Price Allocation [Line Items]
Finite intangible assets, useful life	5 years
Msdsonline One | Trademarks, trade names and domain names | Maximum
Schedule Of Business Acquisitions Purchase Price Allocation [Line Items]
Finite intangible assets, useful life	11 years
Msdsonline One | Non-compete Agreements
Schedule Of Business Acquisitions Purchase Price Allocation [Line Items]
Finite intangible assets, useful life	3 years
Bolt | Customer Lists | Minimum
Schedule Of Business Acquisitions Purchase Price Allocation [Line Items]
Finite intangible assets, useful life	5 years
Bolt | Customer Lists | Maximum
Schedule Of Business Acquisitions Purchase Price Allocation [Line Items]
Finite intangible assets, useful life	11 years
Bolt | Technology
Schedule Of Business Acquisitions Purchase Price Allocation [Line Items]
Finite intangible assets, useful life	5 years
Bolt | Trademarks, trade names and domain names | Minimum
Schedule Of Business Acquisitions Purchase Price Allocation [Line Items]
Finite intangible assets, useful life	5 years
Bolt | Trademarks, trade names and domain names | Maximum
Schedule Of Business Acquisitions Purchase Price Allocation [Line Items]
Finite intangible assets, useful life	11 years
Bolt | Non-compete Agreements
Schedule Of Business Acquisitions Purchase Price Allocation [Line Items]
Finite intangible assets, useful life	3 years
Superior Access | Customer Lists | Minimum
Schedule Of Business Acquisitions Purchase Price Allocation [Line Items]
Finite intangible assets, useful life	5 years
Superior Access | Customer Lists | Maximum
Schedule Of Business Acquisitions Purchase Price Allocation [Line Items]
Finite intangible assets, useful life	11 years
Superior Access | Technology
Schedule Of Business Acquisitions Purchase Price Allocation [Line Items]
Finite intangible assets, useful life	5 years
Superior Access | Trademarks, trade names and domain names | Minimum
Schedule Of Business Acquisitions Purchase Price Allocation [Line Items]
Finite intangible assets, useful life	5 years
Superior Access | Trademarks, trade names and domain names | Maximum
Schedule Of Business Acquisitions Purchase Price Allocation [Line Items]
Finite intangible assets, useful life	11 years
Superior Access | Non-compete Agreements
Schedule Of Business Acquisitions Purchase Price Allocation [Line Items]
Finite intangible assets, useful life	3 years