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Revenue Recognition - Additional Information (Detail) - USD ($)
3 Months Ended
Mar. 31, 2017
Mar. 31, 2016
Jan. 01, 2017
Summary Of Accounting Policies [Line Items]      
Revenue $ 22,841,000 $ 25,439,000  
Topic 606 [Member]      
Summary Of Accounting Policies [Line Items]      
Cumulative-effect adjustment to retained earnings     $ 404,000
Asset impairment charges related to contract assets 0    
Capitalized contract acquisition costs 292,000    
Capitalized contract cost, amortization 141,000    
Impairment loss in relation to costs capitalized 0    
Topic 606 [Member] | Impact of changes in accounting policies, Effect of Change Higher/(Lower) [Member]      
Summary Of Accounting Policies [Line Items]      
Revenue $ 2,759,000