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Goodwill - Additional Information (Detail) (USD $)
3 Months Ended 9 Months Ended
Sep. 30, 2013
Sep. 30, 2012
Mar. 31, 2012
Sep. 30, 2013
Sep. 30, 2012
Dec. 31, 2012
Dec. 31, 2011
Indefinite-lived Intangible Assets [Line Items]              
Carrying amount of goodwill $ 0     $ 0   $ 0 $ 19,800,000
Goodwill and intangible assets impairment 0 20,484,000   0 49,821,000    
Purchases of intangible assets     22,800,000        
Goodwill [Member]
             
Indefinite-lived Intangible Assets [Line Items]              
Goodwill and intangible assets impairment   $ 13,200,000 $ 6,600,000