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Debt - Wells Fargo Credit Agreement - Amendments (Details) - Wells Fargo Credit Agreement - USD ($)
Mar. 29, 2018
Jul. 17, 2017
Apr. 01, 2017
Jan. 27, 2017
Jun. 28, 2016
Dec. 31, 2018
Oct. 01, 2018
Dec. 31, 2017
Oct. 03, 2017
Mar. 31, 2017
Line of Credit Facility [Line Items]                    
Lender fees $ 800,000                 $ 700,000
Revolving Credit Facility                    
Line of Credit Facility [Line Items]                    
Commitment fee percentage 1.00% 1.00%   2.00% 2.00%          
Lender fees           $ 800,000   $ 700,000    
Interest rate increase     2.00%              
Line of credit facility, decrease limit                   25,000,000.0
Available revolving line of credit balance           8,900,000   $ 13,000,000   40,000,000.0
Maximum borrowing capacity $ 75,000,000 $ 52,500,000.0     $ 75,000,000 $ 75,000,000     $ 58,750,000.00 $ 65,000,000
Line of credit facility, increase limit   $ 12,500,000.0         $ 9,000,000.0      
Decrease in interest rate margin   (1.00%)                
Maturity, period prior to senior notes maturity 60 days                  
Percentage of borrowing base 10.00%                  
Revolving Credit Facility | Minimum                    
Line of Credit Facility [Line Items]                    
Line of credit facility, increase limit $ 6,500,000.0               $ 6,250,000.00  
Revolving Credit Facility | Maximum                    
Line of Credit Facility [Line Items]                    
Line of credit facility, increase limit $ 7,500,000.0