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BASIS OF PRESENTATION OF UNAUDITED INTERIM CONDENSED CONSOLIDATED FINANCIAL STATEMENTS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Depreciation (Details) - USD ($)
$ in Millions
3 Months Ended 6 Months Ended
Dec. 31, 2020
Dec. 31, 2020
Accounting Policies [Abstract]    
Depreciation expense, asset retirement obligation $ 1.3 $ 2.6