PROPERTY AND EQUIPMENT (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Total property and equipment cost	$ 1,026,564	$ 939,203
Accumulated depreciation	(627,229)	(571,408)
Total property and equipment	399,335	367,795
Land
Property, Plant and Equipment [Line Items]
Total property and equipment cost	250	250
Medical equipment
Property, Plant and Equipment [Line Items]
Total property and equipment cost	480,631	426,682
Computer and office equipment, furniture and fixtures
Property, Plant and Equipment [Line Items]
Total property and equipment cost	132,446	120,490
Leasehold improvements
Property, Plant and Equipment [Line Items]
Total property and equipment cost	399,253	377,676
Equipment under financing/capital lease
Property, Plant and Equipment [Line Items]
Total property and equipment cost	$ 13,984	$ 14,105