SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Risks and Uncertainties (Details) $ in Millions	12 Months Ended
Dec. 31, 2020 USD ($) site	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Risks and Uncertainties
Number of sites placed in care and maintenance \| site	5
Assets	$ 41,369	$ 39,974	$ 20,715
Conga
Risks and Uncertainties
Assets	$ 1,517	$ 1,558

Sum of the carrying amounts as of the balance sheet date of all assets that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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+ Details