XML 125 R95.htm IDEA: XBRL DOCUMENT v3.10.0.1
Debt (Details Textual) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Senior Notes due 2024    
Debt Instrument [Line Items]    
Net unamortized debt issuance costs $ 4.1 $ 4.9
Silvertip Debt Obligation [Member]    
Debt Instrument [Line Items]    
Letters of Credit Outstanding, Amount 15.0  
Repayments of Debt 12.6  
Letter of Credit [Member]    
Debt Instrument [Line Items]    
Letters of Credit Outstanding, Amount 12.0  
Revolving Credit Facility    
Debt Instrument [Line Items]    
Net unamortized debt issuance costs 2.2 $ 1.9
Line of Credit Facility, Current Borrowing Capacity $ 115.0  
Stated interest rate 4.754%  
Silvertip [Member]    
Debt Instrument [Line Items]    
Letters of Credit Outstanding, Amount $ 100.0