PROPERTY AND EQUIPMENT (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Total property and equipment cost	$ 1,161,222	$ 1,026,564
Accumulated depreciation	(676,975)	(627,229)
Total property and equipment	484,247	399,335
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	560,301	480,631
Computer and office equipment, furniture and fixtures
Property, Plant and Equipment [Line Items]
Total property and equipment cost	144,766	132,446
Leasehold improvements
Property, Plant and Equipment [Line Items]
Total property and equipment cost	441,921	399,253
Equipment under financing/capital lease
Property, Plant and Equipment [Line Items]
Total property and equipment cost	$ 13,984	$ 13,984