SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Government Grants (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		6 Months Ended
	Apr. 30, 2020	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Government Grants [Line Items]
Funding Received From CARES Act	$ 100,000	$ 100,000
Other operating income		22,780	$ 0	$ 22,780	$ 0
Provider relief fund advance		70,000		70,000		$ 0
Estimated Future COVID-19 related expenses				11,000
Funding Received from Massachusetts COVID-19 Provider Sustainability Program				1,000
Equity Method Investments [Member]
Government Grants [Line Items]
Funding Received From CARES Act	2,000	2,000
Home Health and Hospice [Member]
Government Grants [Line Items]
COVID-19 Expenses Incurred				$ 22,000
AseraCare Hospice [Member]
Government Grants [Line Items]
Funding Received From CARES Act	$ 5,000	$ 5,000