ACCOUNTS RECEIVABLE AND ALLOWANCE FOR DOUBTFUL ACCOUNTS - Allowance (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Accounts receivable and allowance for doubtful accounts
Allowance for doubtful accounts as a percent of patients accounts receivable	25.00%		25.40%
Self-Pay Patients
Accounts receivable and allowance for doubtful accounts
Allowance for doubtful accounts as a percent of patients accounts receivable	81.20%		80.60%
Estimated costs of caring	$ 165	$ 164
Managed Care Patients
Accounts receivable and allowance for doubtful accounts
Allowance for doubtful accounts as a percent of patients accounts receivable	8.40%		7.50%
Charity Care Patients
Accounts receivable and allowance for doubtful accounts
Estimated costs of caring	$ 44	36
Medicai DSH and other supplemental revenues
Accounts receivable and allowance for doubtful accounts
Estimated costs of caring	$ 227	$ 247