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Long-Term Debt and Loan Agreements - Additional Information (Details) - USD ($)
1 Months Ended 3 Months Ended
May 30, 2014
Mar. 31, 2017
Mar. 31, 2020
Dec. 31, 2019
Mar. 31, 2019
Debt Instrument [Line Items]          
Long-term Debt     $ 78,000,000 $ 78,000,000  
Long-term Debt     $ 37,338,000 $ 77,176,000  
Weighted average interest rate during period     6.24%   6.23%
Minimum [Member]          
Debt Instrument [Line Items]          
Long-term Debt     $ 11,000,000    
Interest rate     4.67%    
Maximum [Member]          
Debt Instrument [Line Items]          
Long-term Debt     $ 40,000,000    
Interest rate     5.45%    
Senior Unsecured Notes [Member]          
Debt Instrument [Line Items]          
Long-term Debt     $ 78,000,000    
Loan Agreement [Member]          
Debt Instrument [Line Items]          
Maximum borrowing capacity on line of credit   $ 200,000,000      
Loan maturity period 2018-12 2022-03      
Remaining amount available under the line of credit     194,200,000    
Letters of credit     5,800,000    
Loan Agreement [Member] | EPA [Member]          
Debt Instrument [Line Items]          
Financial assurance required to be provided     $ 2,000,000