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Stockholders' Equity - Additional Information (Detail) (USD $)
In Millions, except Share data, unless otherwise specified
9 Months Ended
Sep. 30, 2013
Sep. 30, 2012
Dec. 31, 2012
Equity [Abstract]      
Additional repurchased shares     1,000,000
Shares remain available for repurchase from the announced authorization 1,030,438   30,438
Repurchased shares 0 0  
Share repurchased relating to tax withholding requirements $ 1.3 $ 1.0  
Repurchased shares tax withholding 48,937 53,019