ACCOUNTS RECEIVABLE - Allowance (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Accounts receivable and allowance for doubtful accounts
Estimated costs of caring	$ 195	$ 212	$ 579	$ 609
Uninsured patients
Accounts receivable and allowance for doubtful accounts
Estimated costs of caring	165	171	466	493
Charity care patients
Accounts receivable and allowance for doubtful accounts
Estimated costs of caring	$ 30	$ 41	$ 113	$ 116

Total expenses of a HCO before stop-loss insurance recoveries. Costs of services rendered (including costs of services rendered but not yet reported).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 954
-SubTopic 450
-Section 30
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=68049836&loc=d3e5919-115623

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 954
-SubTopic 405
-Section 25
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=68064407&loc=d3e4590-115610

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 954
-SubTopic 450
-Section 30
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=68049836&loc=d3e5910-115623

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration