Consolidated Financial Statements - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	9 Months Ended
Sep. 30, 2012	Sep. 30, 2011
Significant Accounting Policies [Line Items]
Prior period reclassified amount from stock-based compensation to changes in other liabilities	$ 2.8
Allowance for doubtful accounts		2.1
Increase in trade accounts receivable and the related allowance for doubtful accounts		$ 2.1

The amount of a reclassification adjustment made to prior period financial statement amounts.

No definition available.

Name:	us-gaap_PriorPeriodReclassificationAdjustment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration