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Management - Labor Relations (Details) | 12 Months Ended
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Dec. 31, 2020 numberOfEmployee numberOfMine
Concentration Risk [Line Items] |
Number of employees | 4,600
Number of hourly employees | 3,500
Hourly employees represented by organized labor unions (in percent) | 29.00%
Coal production generated by hourly employees represented by organized labor unions (in percent) | 18.00%
Number of us mines represented by unions | numberOfMine | 1
Period of agreement with UMWA covering hourly coworkers involved in mining reclamation | 4 years
Wilpinjong Employees |
Concentration Risk [Line Items] |
Australian hourly employees under contract negotiations (in percent) | 39.00%
Coal production generated by Australian hourly employees under contract negotiation (in percent) | 59.00%
Moorvale Employees |
Concentration Risk [Line Items] |
Australian hourly employees under contract negotiations (in percent) | 15.00%
Coal production generated by Australian hourly employees under contract negotiation (in percent) | 5.00%
Metropolitan Employees |
Concentration Risk [Line Items] |
Australian hourly employees under contract negotiations (in percent) | 14.00%
Coal production generated by Australian hourly employees under contract negotiation (in percent) | 4.00%
Wambo Operation Employees |
Concentration Risk [Line Items] |
Australian hourly employees under contract negotiations (in percent) | 8.00%
Coal production generated by Australian hourly employees under contract negotiation (in percent) | 23.00%
Coppabella/Moorvale Employees |
Concentration Risk [Line Items] |
Australian hourly employees under contract negotiations (in percent) | 23.00%
Coal production generated by Australian hourly employees under contract negotiation (in percent) | 9.00%
Shoal Creek |
Concentration Risk [Line Items] |
Coal production generated by hourly employees (in percent) | 1.00%

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