Annual report pursuant to Section 13 and 15(d)

BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES- Cash Equivalents and Restricted Cash (Details)

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BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES- Cash Equivalents and Restricted Cash (Details) - Cripple Creek Project - USD ($)
$ in Millions
Jan. 31, 2022
Dec. 31, 2021
Feb. 12, 2021
Basis Of Presentation [Line Items]      
Restricted cash account     $ 180.0
Restricted cash reserved   $ 176.6  
Subsequent Event      
Basis Of Presentation [Line Items]      
Restricted cash reserved $ 221.0