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           Soft Dollar Arrangements - Additional Information (Detail) (USD $) 
        In Thousands, unless otherwise specified  | 
        3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
| 
           Jun. 30, 2014 
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           Jun. 30, 2013 
         | 
        
           Jun. 30, 2014 
         | 
        
           Jun. 30, 2013 
         | 
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| Soft Dollar Arrangements [Abstract] | ||||
| Soft dollar credits | $ 263 | $ 248 | $ 527 | $ 496 | 
| X | ||||||||||
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- Details 
          
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- Definition 
          Soft dollar credits. No definition available. 
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