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Long-Term Debt - Additional Information (Detail)
 12 Months Ended
Nov. 06, 2015
USD ($)
Dec. 31, 2015
USD ($)
Dec. 31, 2014
USD ($)
Dec. 31, 2013
USD ($)
Debt Instrument [Line Items]        
Revolving credit facility, drawn down amount   $ 6,000,000 $ 53,000,000 $ 145,000,000
Finance cost capitalized   1,500,000 2,600,000 2,500,000
Amortization of deferred finance costs   $ 1,200,000 $ 700,000 400,000
Maximum ratio of net debt to EBITDA   3.0    
Minimum ratio of EBITDA to net interest   4.0    
Weighted average rate of interest on borrowings   0.0167% 1.70%  
Payments of interest on long-term debt   $ 2,300,000 $ 2,300,000 1,000,000
Net cash outflows in respect of refinancing costs   $ 1,500,000 $ 100,000 $ 900,000
Revolving Credit Facility [Member]        
Debt Instrument [Line Items]        
Credit facility maximum borrowing capacity $ 200,000,000      
Expiration date of facility   Nov. 30, 2020    
Finance cost capitalized   $ 1,500,000    
Maximum Additional Amount to be Committed by Lenders [Member]        
Debt Instrument [Line Items]        
Revolving credit facility, drawn down amount $ 50,000,000