Long-Term Cash Incentive Plan - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	9 Months Ended
Sep. 30, 2012	Dec. 31, 2011
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Estimated payment of plan including employer costs	$ 2.7
Accrued compensation expense	2.5	1.8
2010 LTIP
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Accrued compensation expense	$ 0.6	$ 1.1

Aggregate carrying value as of the balance sheet date of the liabilities for deferred compensation arrangements. Represents currently earned compensation under cash arrangements (such as a profit-sharing plan, rabbi trust, and employee contract--excluding equity-based arrangements) that is not actually paid until a later date.

No definition available.

Name:	us-gaap_DeferredCompensationCashbasedArrangementsLiabilityCurrentAndNoncurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant