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Long-term Debt (Details) - USD ($)
$ in Millions
3 Months Ended
May 11, 2020
Aug. 07, 2017
Mar. 31, 2020
Dec. 31, 2019
Revolving Credit Facility        
Revolving credit facility, remaining borrowing capacity     $ 1.8  
Letters of credit outstanding     8.2  
Revolving Credit Facility [Member]        
Revolving Credit Facility        
Revolving credit facility, maximum borrowing capacity   $ 200.0 200.0  
Revolving credit facility contingent increase in maximum borrowing capacity   $ 200.0 $ 200.0  
Weighted-average interest rate (as a percent)     1.64% 2.64%
Revolving credit facility, amount outstanding     $ 190.0  
Revolving Credit Facility [Member] | Subsequent Events.        
Revolving Credit Facility        
Interest rate added to base rate (as a percent) 1.50%      
Percentage of commitment fee on unused credit facility 0.25%      
Revolving credit facility, amount outstanding $ 190.0      
Line Of Credit Facility, Increase In Borrowing Capacity $ 82.5      
Revolving Credit Facility [Member] | Minimum        
Revolving Credit Facility        
Percentage of commitment fee on unused credit facility   0.125%    
Revolving Credit Facility [Member] | Maximum        
Revolving Credit Facility        
Percentage of commitment fee on unused credit facility   0.30%    
Revolving Credit Facility [Member] | LIBOR | Minimum        
Revolving Credit Facility        
Interest rate added to base rate (as a percent)   0.875%    
Revolving Credit Facility [Member] | LIBOR | Maximum        
Revolving Credit Facility        
Interest rate added to base rate (as a percent)   1.875%    
Revolving Credit Facility [Member] | Federal Reserve Bank of New York        
Revolving Credit Facility        
Interest rate added to base rate (as a percent)   0.50%    
Revolving Credit Facility [Member] | Adjusted Eurodollar Rate        
Revolving Credit Facility        
Interest rate added to base rate (as a percent)   1.00%    
Interest period   1 month