Annual report pursuant to Section 13 and 15(d)

Employee Benefit Plan - Additional Information (Detail)

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Employee Benefit Plan - Additional Information (Detail) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Defined Benefit Plan Disclosure [Line Items]      
Percentage of matching contribution of each participants 100.00% 100.00% 100.00%
Maximum contribution percentage of participating employees 6.00% 5.00% 5.00%
Company's contribution to the 401K plan $ 2.1 $ 1.8 $ 1.4