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Goodwill and Other Intangible Assets - Additional Information (Detail) (USD $)
 12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Intangible Assets [Line Items]      
Goodwill Acquired   $ 30,659,000  
Intangible assets, Amortization expense 1,600,000 1,300,000 500,000
Mode
      
Intangible Assets [Line Items]      
Goodwill Acquired   29,389,000  
Weighted average life of definite lived intangible assets 16 years 3 months    
Hub
      
Intangible Assets [Line Items]      
Goodwill Acquired   $ 1,270,000  
Weighted average life of definite lived intangible assets 7 years 22 days