Quarterly report pursuant to Section 13 or 15(d)

Debt (Details)

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Debt (Details) - USD ($)
1 Months Ended 3 Months Ended 9 Months Ended
Jan. 31, 2015
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Dec. 31, 2016
Long-term Debt, Fiscal Year Maturity [Abstract]            
Debt outstanding   $ 182,100,000   $ 182,100,000   $ 216,300,000
Deferred financing costs   1,300,000   $ 1,300,000   1,700,000
LIBOR            
Long-term Debt, Fiscal Year Maturity [Abstract]            
Base margin       2.00%    
Base Rate            
Long-term Debt, Fiscal Year Maturity [Abstract]            
Base margin       0.75%    
Term Loan Facility            
Long-term Debt, Fiscal Year Maturity [Abstract]            
Term loan payments 2017   5,600,000   $ 5,600,000    
Term loan payments 2018   28,100,000   28,100,000    
Term loan payments 2019   30,000,000   30,000,000    
Term loan payments 2020   36,300,000   36,300,000    
Borrowings outstanding   100,000,000   100,000,000    
Revolving Loan Facility            
Long-term Debt, Fiscal Year Maturity [Abstract]            
Revolving loans maximum borrowing capacity   150,000,000   150,000,000    
Revolving loans amount outstanding   82,100,000   82,100,000   100,400,000
Letters of credit outstanding   $ 0   0   $ 0
Amended and Restated            
Long-term Debt, Fiscal Year Maturity [Abstract]            
Revolving Loans, Potential Increment in Maximum Borrowing Capacity       $ 75,000,000    
Amortization period of debt issuance costs 5 years          
Duration of interest rate cash flow hedge 3 years          
Effective interest rate   3.36%   3.36%    
Interest expense, net   $ 1,800,000 $ 2,000,000 $ 5,600,000 $ 5,800,000  
Amended and Restated | Minimum            
Long-term Debt, Fiscal Year Maturity [Abstract]            
Interest rate range   3.24%   3.24%    
Amended and Restated | Maximum            
Long-term Debt, Fiscal Year Maturity [Abstract]            
Interest rate range   5.00%   5.00%    
Amended and Restated | Swap            
Long-term Debt, Fiscal Year Maturity [Abstract]            
Derivative notional amount   $ 85,000,000   $ 85,000,000