Annual report pursuant to Section 13 and 15(d)

Employee Benefit Plans - Additional Information (Detail)

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Employee Benefit Plans - Additional Information (Detail) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Employee Benefits Disclosure [Line Items]      
Contributions to employee benefit plans $ 0.9 $ 0.7 $ 0.5