NET OPERATING REVENUES - Sources of Net Operating Revenue (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Disaggregation of Revenue [Line Items]
Net operating revenues	$ 3,648	$ 4,560	$ 8,168	$ 9,105
Effect of Change in Accounting Principle
Disaggregation of Revenue [Line Items]
Net operating revenues			5	17
Ambulatory Care
Disaggregation of Revenue [Line Items]
Net operating revenues	368	524	858	1,004
Conifer
Disaggregation of Revenue [Line Items]
Net operating revenues	305	355	637	704
Operating segments | Hospital Operations
Disaggregation of Revenue [Line Items]
Net operating revenues	3,088	3,827	6,922	7,689
Operating segments | Ambulatory Care
Disaggregation of Revenue [Line Items]
Net operating revenues	368	524	858	1,004
Operating segments | Conifer
Disaggregation of Revenue [Line Items]
Net operating revenues	305	355	637	704
Inter-segment eliminations
Disaggregation of Revenue [Line Items]
Net operating revenues	(113)	(146)	(249)	(292)
Continuing operations:
Disaggregation of Revenue [Line Items]
Net operating revenues	3,648	4,560	8,168	9,105
Continuing operations: | Operating segments | Hospital Operations
Disaggregation of Revenue [Line Items]
Net operating revenues	3,088	3,827	6,922	7,689
Continuing operations: | Operating segments | Hospital Operations | Other Revenues
Disaggregation of Revenue [Line Items]
Net operating revenues	259	280	553	560
Continuing operations: | Operating segments | Ambulatory Care
Disaggregation of Revenue [Line Items]
Net operating revenues	368	524	858	1,004
Continuing operations: | Operating segments | Conifer
Disaggregation of Revenue [Line Items]
Net operating revenues	305	355	637	704
Continuing operations: | Inter-segment eliminations
Disaggregation of Revenue [Line Items]
Net operating revenues	(113)	(146)	(249)	(292)
Continuing operations: | Acute Care Hospitals and Related Outpatient Facilities | Operating segments | Hospital Operations | Medicare
Disaggregation of Revenue [Line Items]
Net operating revenues	597	721	1,302	1,479
Continuing operations: | Acute Care Hospitals and Related Outpatient Facilities | Operating segments | Hospital Operations | Medicaid
Disaggregation of Revenue [Line Items]
Net operating revenues	259	316	540	630
Continuing operations: | Acute Care Hospitals and Related Outpatient Facilities | Operating segments | Hospital Operations | Managed care
Disaggregation of Revenue [Line Items]
Net operating revenues	1,824	2,330	4,145	4,684
Continuing operations: | Acute Care Hospitals and Related Outpatient Facilities | Operating segments | Hospital Operations | Uninsured
Disaggregation of Revenue [Line Items]
Net operating revenues	22	11	62	12
Continuing operations: | Acute Care Hospitals and Related Outpatient Facilities | Operating segments | Hospital Operations | Indemnity and other
Disaggregation of Revenue [Line Items]
Net operating revenues	127	169	320	324
Continuing operations: | Acute Care Hospitals and Related Outpatient Facilities | Operating segments | Hospital Operations | Total
Disaggregation of Revenue [Line Items]
Net operating revenues	$ 2,829	$ 3,547	$ 6,369	$ 7,129