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Management - Labor Relations Labor Relations (Details) | 12 Months Ended
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Dec. 31, 2019
Concentration Risk [Line Items] |
Entity Number of Employees | 6,600
Entity Number Of Hourly Employees | 5,000
Percentage of hourly employees represented by organized labor unions | 42.00%
Percentage Of Coal Production Generated By Hourly Employees Represented By Organized Labor Unions | 19.00%
Number of US Mines Represented by Unions | 2
Millenium Employees |
Concentration Risk [Line Items] |
Percentage Of Australian Hourly Employees Under Contract Negotiations | 1.00%
Percentage Of Coal Production Generated By Australian Hourly Employees Under Contract Negotiation | 2.00%
Wilpinjong Employees |
Concentration Risk [Line Items] |
Percentage Of Australian Hourly Employees Under Contract Negotiations | 25.00%
Percentage Of Coal Production Generated By Australian Hourly Employees Under Contract Negotiation | 54.00%
Moorvale Employees |
Concentration Risk [Line Items] |
Percentage Of Australian Hourly Employees Under Contract Negotiations | 14.00%
Percentage Of Coal Production Generated By Australian Hourly Employees Under Contract Negotiation | 6.00%
Metropolitan Employees |
Concentration Risk [Line Items] |
Percentage Of Australian Hourly Employees Under Contract Negotiations | 14.00%
Percentage Of Coal Production Generated By Australian Hourly Employees Under Contract Negotiation | 6.00%
Wambo Operation Employees |
Concentration Risk [Line Items] |
Percentage Of Australian Hourly Employees Under Contract Negotiations | 24.00%
Percentage Of Coal Production Generated By Australian Hourly Employees Under Contract Negotiation | 22.00%
Coppabella/Moorvale Employees |
Concentration Risk [Line Items] |
Percentage Of Australian Hourly Employees Under Contract Negotiations | 22.00%
Percentage Of Coal Production Generated By Australian Hourly Employees Under Contract Negotiation | 9.00%
Kayenta Mine | United Mine Workers of America |
Concentration Risk [Line Items] |
Percentage Of Coal Production Generated By Hourly Employees | 3.00%
Shoal Creek |
Concentration Risk [Line Items] |
Percentage Of Coal Production Generated By Hourly Employees | 1.00%
Shoal Creek | United Mine Workers of America |
Concentration Risk [Line Items] |
Percentage of hourly employees represented by organized labor unions | 11.00%

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