ACCOUNTS RECEIVABLE - Allowance (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Accounts receivable and allowance for doubtful accounts
Estimated costs of caring	$ 196	$ 192
Uninsured patients
Accounts receivable and allowance for doubtful accounts
Estimated costs of caring	156	158
Charity care patients
Accounts receivable and allowance for doubtful accounts
Estimated costs of caring	$ 40	$ 34

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

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