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Debt - Additional Information (Detail) - USD ($)
12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Jan. 28, 2016
Oct. 31, 2012
Debt Instrument [Line Items]        
Debt outstanding $ 0 $ 0    
Revolver [Member]        
Debt Instrument [Line Items]        
Revolving credit facility, interest rate description LIBOR + 2.00% per annum (for LIBOR loans) or the greater of 1.00% or the bank's prime rate minus 0.50% per annum (for base rate loans)      
Unused credit facility fee 0.25%      
Borrowings under revolver $ 0 $ 0    
Revolver [Member] | LIBOR Loans [Member]        
Debt Instrument [Line Items]        
Revolving credit facility, interest rate description LIBOR + 2.00% per annum (for LIBOR loans)      
Spread on variable rate 2.00%      
Revolver [Member] | Base Rate Loans [Member]        
Debt Instrument [Line Items]        
Revolving credit facility, interest rate description The greater of 1.00% or the bank's prime rate minus 0.50% per annum (for base rate loans)      
Base rate 1.00%      
Spread on variable rate (0.50%)      
2012 Revolver [Member]        
Debt Instrument [Line Items]        
Amount of revolving credit facility       $ 10,000,000
Expiry period of revolver 3 years      
Date of expiry Oct. 16, 2015      
2012 Revolver [Member] | Extended Expiration [Member]        
Debt Instrument [Line Items]        
Date of expiry Jan. 31, 2016      
2016 Revolver [Member]        
Debt Instrument [Line Items]        
Amount of revolving credit facility     $ 20,000,000  
Date of expiry Jan. 28, 2019