ORGANIZATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Effect of Topic 606 on Statement of Operations (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Condensed Consolidated Statement of Operations
Net revenue	$ 233,995
Other operating costs	31,096	$ 32,689
Income from operations	623	(9,541)
Loss from operations before income taxes	(28,814)	(23,734)
Net loss	(22,618)	(17,734)
Comprehensive loss	(25,200)	(17,751)
Before adoption of ASC 606 | ASU 2014-09
Condensed Consolidated Statement of Operations
Net revenue	234,893
Other operating costs	31,964
Income from operations	653
Loss from operations before income taxes	(28,784)
Net loss	(22,588)
Comprehensive loss	(25,170)
Adjustments | ASU 2014-09
Condensed Consolidated Statement of Operations
Net revenue	898
Other operating costs	868
Income from operations	30
Loss from operations before income taxes	30
Net loss	30
Comprehensive loss	30
Cranial revenue from satisfying performance obligations coming from previous period	1,000
Estimated uncollectible amounts due from self-pay patients	900
Patient Care
Condensed Consolidated Statement of Operations
Net revenue	188,507
Income from operations	17,093	14,543
Loss from operations before income taxes	9,104	6,380
Net loss	9,104	6,380
Patient Care | Before adoption of ASC 606
Condensed Consolidated Statement of Operations
Net revenue		187,637
Patient Care | Adjustments | ASU 2014-09
Condensed Consolidated Statement of Operations
Net revenue		$ (900)
Cranial revenue deferred	$ 1,100