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Related Party Transactions - Additional Information (Detail) - USD ($)
12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Related Party Transaction [Line Items]    
Purchase of non-controlling interests $ 224,000 $ 409,000
Treasury stock, shares 1,542,894 1,531,713
Partnership And Trust [Member]    
Related Party Transaction [Line Items]    
Purchase of non-controlling interests $ 224,000 $ 409,000
Related Party [Member]    
Related Party Transaction [Line Items]    
Treasury stock, shares 10,000 10,000