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Debt - Additional Information (Detail)
$ in Thousands
9 Months Ended
Jun. 18, 2014
USD ($)
Instruments
Sep. 30, 2014
Sep. 30, 2017
USD ($)
Dec. 31, 2016
USD ($)
Debt Instrument [Line Items]        
Maximum principal borrowing amount $ 225,000      
Letter of credit, sub-limit amount $ 15,000      
Credit facility scheduled to expire   Jun. 18, 2019    
Line of credit facility, description   (a) the Federal Funds Rate in effect on such day plus 0.5% (b) the Prime Rate in effect on such day and (c) the Eurodollar Rate for a one month interest period on such day plus 1.0%, plus a margin ranging from 0.75% to 1.5% per annum or Eurodollar rate plus a margin ranging from 1.75% to 2.5% per annum. Swing line loans bear interest at the Base Rate.    
Line of credit facility drawn     $ 119,000 $ 87,000
Letter of credit outstanding     11,000  
Available credit under agreement     $ 95,000  
Minimum        
Debt Instrument [Line Items]        
Commitment fee rates for unused commitments 0.225%      
Maximum        
Debt Instrument [Line Items]        
Commitment fee rates for unused commitments 0.375%      
Federal funds rate        
Debt Instrument [Line Items]        
Line of credit facility interest rate 0.50%      
Eurodollar        
Debt Instrument [Line Items]        
Line of credit facility interest rate 1.00% 3.24%    
Line of credit facility, borrowing outstanding | Instruments 15      
Eurodollar | Minimum        
Debt Instrument [Line Items]        
Line of credit facility interest rate 1.75%      
Eurodollar | Maximum        
Debt Instrument [Line Items]        
Line of credit facility interest rate 2.50%      
Base rate        
Debt Instrument [Line Items]        
Line of credit facility interest rate   5.25%    
Base rate | Minimum        
Debt Instrument [Line Items]        
Line of credit facility interest rate 0.75%      
Base rate | Maximum        
Debt Instrument [Line Items]        
Line of credit facility interest rate 1.50%