SIGNIFICANT ACCOUNTING POLICIES - Investments in Unconsolidated Affiliates (Details) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2015 Institution	Dec. 31, 2016 USD ($) Institution	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Schedule of Equity Method Investments [Line Items]
Current assets		$ 943.0	$ 866.0
Noncurrent assets		991.0	854.0
Current liabilities		(320.0)	(301.0)
Noncurrent liabilities		(345.0)	(377.0)
Noncontrolling interests		(494.0)	(309.0)
Net operating revenues		2,823.0	1,335.0
Net income		573.0	436.0
Net income attributable to the investee		$ 343.0	356.0
Number of hospitals | Institution	90
Number of outpatient centers | Institution		470
Income (Loss) from Equity Method Investments		$ 131.0	99.0	$ 12.0
Investee results reflected (as a percentage)		100
Texas Health Ventures Group, LLC
Schedule of Equity Method Investments [Line Items]
Income (Loss) from Equity Method Investments		$ 61.0	$ 35.0
Ambulatory Care
Schedule of Equity Method Investments [Line Items]
Number of outpatient centers | Institution		323
Number of outpatient centers recorded using equity method | Institution		108
Number of outpatient centers recorded not using equity method | Institution		215
Hospital operations and other
Schedule of Equity Method Investments [Line Items]
Number of outpatient centers recorded using equity method | Institution		12
Number of hospitals recorded using equity method | Institution		4