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Line of Credit - Additional Information (Details) - Revolving Credit Facility - Bank of America, N.A, - USD ($)
12 Months Ended
Mar. 23, 2016
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Line Of Credit Facility [Line Items]        
Line of credit facility agreement date Mar. 23, 2016      
Line of credit facility expiration date Mar. 23, 2021      
Maximum amount of line of credit $ 75,000,000      
Line of credit facility interest rate description   Borrowings under the credit agreement accrue interest, at our option, at (1) a base rate equal to the highest of (a) the federal funds rate plus 0.50%, (b) the prime rate and (c) the LIBOR rate plus 1.00%, in each case plus a margin ranging from 0.25% to 0.75%, or (2) an adjusted LIBOR rate plus a margin ranging from 1.25% to 1.75%.    
Outstanding borrowings   $ 0 $ 0 $ 15,100,000
Weighted-average interest rate of debt outstanding       5.00%
Line of credit facility, additional maximum borrowing capacity 25,000,000      
Line of credit facility, additional borrowing capacity initial minimum amount 10,000,000      
Line of credit facility, additional borrowing capacity increments thereafter $ 5,000,000      
Line of credit facility, asset restrictions   The credit agreement also contains customary covenants restricting our activities, including limitations on our ability to sell assets, engage in mergers and acquisitions, enter in transactions involving related parties, obtain letters of credit, incur indebtedness or grant liens or negative pledges on our assets, make loans or make other investments.    
Line of credit facility, dividend restrictions   prohibited from paying cash dividends with respect to our capital stock    
Federal Funds Rate        
Line Of Credit Facility [Line Items]        
Basis spread on variable rate (as a percent) 0.50%      
London Interbank Offered Rate (LIBOR)        
Line Of Credit Facility [Line Items]        
Basis spread on variable rate (as a percent) 1.00%      
Margin Rate | Minimum        
Line Of Credit Facility [Line Items]        
Basis spread on variable rate (as a percent) 0.25%      
Margin Rate | Maximum        
Line Of Credit Facility [Line Items]        
Basis spread on variable rate (as a percent) 0.75%      
LIBOR Rate Margin | Minimum        
Line Of Credit Facility [Line Items]        
Basis spread on variable rate (as a percent) 1.25%      
LIBOR Rate Margin | Maximum        
Line Of Credit Facility [Line Items]        
Basis spread on variable rate (as a percent) 1.75%