XML 63 R53.htm IDEA: XBRL DOCUMENT v3.19.1
Long-term Debt (Narrative) (Details) - USD ($)
1 Months Ended 9 Months Ended 12 Months Ended
Apr. 04, 2017
Mar. 31, 2019
Sep. 30, 2018
Dec. 31, 2018
Dec. 31, 2017
Debt Instrument [Line Items]          
Increase option $ 100,000,000.0        
Default interest rate above applicable interest rate     2.00%    
Revolving credit facility          
Debt Instrument [Line Items]          
Revolving credit facility used 400,000,000        
Interest rate at period end     3.63%    
Remaining borrowing capacity     $ 150,200,000    
Letter Of Credit          
Debt Instrument [Line Items]          
Revolving credit facility used $ 15,000,000        
LIBOR Rate | Minimum | Revolving credit facility          
Debt Instrument [Line Items]          
Basis spread on variable rate 1.25%        
LIBOR Rate | Maximum | Revolving credit facility          
Debt Instrument [Line Items]          
Basis spread on variable rate 2.25%        
Credit Agreement Base Rate | Minimum | Revolving credit facility          
Debt Instrument [Line Items]          
Basis spread on variable rate 0.25%        
Credit Agreement Base Rate | Maximum | Revolving credit facility          
Debt Instrument [Line Items]          
Basis spread on variable rate 1.25%        
Line of Credit | Revolving credit facility          
Debt Instrument [Line Items]          
Revolving credit facility used     249,830,000   $ 249,830,000
Outstanding revolving credit facility     $ 247,000,000   $ 247,000,000
Subsequent Event          
Debt Instrument [Line Items]          
Payments for credit accommodations   $ 100,000   $ 800,000