Long-Term Cash Incentive Plan - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Accrued compensation expense	$ 2.6	$ 1.8
Eligible payment made under the plan	2.3
Long Term Incentive Plan Twenty Thirteen [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Estimated payment of plan including employer cost	5.8
Long Term Incentive Plan Twenty Ten [Member]
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Accrued compensation expense	$ 0.8	$ 1.1