SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Changes to Goodwill (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
Mar. 31, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Goodwill [Roll Forward]
Goodwill, Beginning Balance	$ 87	$ 87	$ 87	$ 87
Impairments		(87)	0	0
Goodwill, Ending Balance		0	87	87
Egypt
Goodwill [Roll Forward]
Goodwill, Beginning Balance	87	87	87	87
Impairments	$ (87)	(87)	0	0
Goodwill, Ending Balance		$ 0	$ 87	$ 87

Amount of loss from the write-down of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
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-URI http://asc.fasb.org/extlink&oid=121556970&loc=d3e13854-109267

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
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-URI http://asc.fasb.org/extlink&oid=99380562&loc=d3e13777-109266

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration