ORGANIZATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Patient Care (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018 USD ($) item	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($) item	Sep. 30, 2017 USD ($)
Summary of Significant Accounting Policies
Net revenues	$ 262,946	$ 257,966	$ 763,907	$ 755,033
ASU 2014-09 | Before adoption of ASC 606
Summary of Significant Accounting Policies
Net revenues	$ 263,591		$ 766,773
Patient Care
Summary of Significant Accounting Policies
Labor warranty			90 days
Manufacturer warranty			180 days
Number of performance obligations | item	2		2
Maximum cranial device follow up visit period			90 days
Net revenues	$ 214,080	210,637	$ 620,745	614,495
Patient Care | Before adoption of ASC 606
Summary of Significant Accounting Policies
Net revenues		210,637		614,495
Patient Care | ASU 2014-09
Summary of Significant Accounting Policies
Net revenue deferred	1,000		1,000
Revenue recognized from satisfying performance obligations coming from previous period			1,000
Patient Care | Medicare
Summary of Significant Accounting Policies
Net revenues	69,724		197,461
Patient Care | Medicare | Before adoption of ASC 606
Summary of Significant Accounting Policies
Net revenues		65,759		186,606
Patient Care | Medicaid
Summary of Significant Accounting Policies
Net revenues	33,597		96,993
Patient Care | Medicaid | Before adoption of ASC 606
Summary of Significant Accounting Policies
Net revenues		32,557		95,524
Patient Care | Commercial Insurance/ Managed Care (excluding Medicare and Medicaid Managed Care)
Summary of Significant Accounting Policies
Net revenues	78,333		226,761
Patient Care | Commercial Insurance/ Managed Care (excluding Medicare and Medicaid Managed Care) | Before adoption of ASC 606
Summary of Significant Accounting Policies
Net revenues		79,804		234,866
Patient Care | Veterans Administration
Summary of Significant Accounting Policies
Net revenues	19,317		56,873
Patient Care | Veterans Administration | Before adoption of ASC 606
Summary of Significant Accounting Policies
Net revenues		18,662		52,995
Patient Care | Private Pay
Summary of Significant Accounting Policies
Estimated uncollectible amounts	600		2,900
Net revenues	$ 13,109		$ 42,657
Patient Care | Private Pay | Before adoption of ASC 606
Summary of Significant Accounting Policies
Net revenues		$ 13,855		$ 44,504