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Debt - Additional Information (Detail)
$ in Thousands
 1 Months Ended 12 Months Ended
Jun. 30, 2016
USD ($)
Dec. 10, 2012
USD ($)
Jun. 30, 2016
USD ($)
Dec. 31, 2017
USD ($)
Dec. 31, 2016
USD ($)
Nov. 30, 2012
USD ($)
Disclosure Of Borrowings [Line Items]            
Net Debt to EBITDA ratio       0.9 (1.7)  
Revolving credit facility [member]            
Disclosure Of Borrowings [Line Items]            
Borrowings           $ 375,000
Current net leverage ratio       0.9    
LIBOR interest plus margin       2.00%    
Loan undrawn standby fee       0.50%    
Loan undrawn standby fee paid $ 2,031          
Prepaid loan cost       $ 1,272 $ 1,772  
Revolving credit facility [member] | Amended and restated credit agreement [member]            
Disclosure Of Borrowings [Line Items]            
Borrowings 250,000   $ 250,000      
Additional borrowing capacity $ 100,000   $ 100,000      
Borrowings maturity     Jun. 13, 2020      
Aggregate unsecured indebtedness       850,000    
Secured indebtedness incurred       200,000    
Unsecured indebtedness       $ 150,000    
Net Debt to EBITDA ratio       3.5    
Minimum EBITDA to Interest ratio       3    
Loan undrawn standby fee paid       $ 0    
Senior notes [member]            
Disclosure Of Borrowings [Line Items]            
Borrowings maturity   Dec. 15, 2020        
Senior notes issued   $ 589,500        
Notes issued at par value   $ 600,000        
Notes issued coupon rate   6.125%        
Principal amount notes redemption price       At any time prior to December 15, 2016 at a redemption price equal to 100% of the aggregate principal amount of the notes at the treasury yield plus 50 basis points, and any accrued and unpaid interest    
Fair market value of notes issued       $ 596,000    
Deferred financing cost       $ 6,217 $ 8,411