Quarterly report pursuant to Section 13 or 15(d)

Income Taxes - Additional Information (Detail)

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Income Taxes - Additional Information (Detail) (USD $)
In Millions, unless otherwise specified
6 Months Ended
Jun. 30, 2012
Jun. 30, 2011
Dec. 31, 2011
Income Taxes [Line Items]      
Increase in unrecognized tax benefits $ 0.30 $ 0.08  
Liabilities for unrecognized tax benefits     3.9
Unrecognized tax benefit, related interest accrued net of federal income tax benefits     0.1
Unrecognized tax benefits, related penalty     0.02
Valuation allowance to offset deferred tax asset $ 0.2