XML 78 R62.htm IDEA: XBRL DOCUMENT v3.19.1
LONG-TERM DEBT AND OTHER FINANCING ARRANGEMENTS 2023 revolving credit facility, narrative (Details) - USD ($)
$ in Thousands
Mar. 31, 2019
Dec. 31, 2018
2023 Revolving Credit Facility [Member]    
Debt Instrument [Line Items]    
Long-term Line of Credit, Noncurrent $ 0  
Line of credit facility, maximum borrowing capacity $ 75,000  
2023 Revolving Credit Facility [Member] | Eurodollar [Member]    
Debt Instrument [Line Items]    
Derivative, Basis Spread on Variable Rate 1.00%  
CME NV and CME BV [Member]    
Debt Instrument [Line Items]    
Outstanding Shares Pledged, Percentage 100.00%  
CME NV and CME BV [Member] | 2023 Revolving Credit Facility [Member]    
Debt Instrument [Line Items]    
Outstanding Shares Pledged, Percentage   100.00%