Acquisitions - Summary of Purchase Price Allocations Initially Recorded on Consolidated Balance Sheet for all Acquisitions (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2013
Loans At Acquisition Date [Line Items]
Cash acquired	$ 2.9
Goodwill expected to be deductible for tax purposes	18.1
Weighted-average life of the identifiable definite-lived intangible assets	8 years 3 months 18 days
Developed Technology [Member]
Loans At Acquisition Date [Line Items]
Identifiable definite-lived intangible assets	1.6
Trade Name [Member]
Loans At Acquisition Date [Line Items]
Identifiable definite-lived intangible assets	7.0
Customer Relationships [Member]
Loans At Acquisition Date [Line Items]
Identifiable definite-lived intangible assets	7.9
Non-Compete Agreements [Member]
Loans At Acquisition Date [Line Items]
Identifiable definite-lived intangible assets	$ 0.4