Acquisitions - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2012 Y	Jul. 28, 2011
Business Acquisition [Line Items]
Business acquisition, cash paid		$ 10.6
Fair value of contingent consideration		0.9
Contingent consideration expiration year	2015
Period for performance evaluation, years	4
Business acquisition, effective date	Jul. 28, 2011
Other Noncurrent Liabilities
Business Acquisition [Line Items]
Fair value of contingent consideration	1.1
Maximum
Business Acquisition [Line Items]
Potential cash payment to shareholders	12.0