ORGANIZATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Segment (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018 USD ($) item	Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($) item	Jun. 30, 2017 USD ($)
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	$ 266,966	$ 263,386	$ 500,961	$ 497,067
Patient Care
Summary of Significant Accounting Policies
Net revenues	218,158	216,221	406,665	403,858
Patient Care | Operating segments
Summary of Significant Accounting Policies
Net revenues	218,158	216,221	406,665	403,858
Patient Care | Before adoption of ASC 606
Summary of Significant Accounting Policies
Net revenues		216,221		403,858
Patient Care | Medicare
Summary of Significant Accounting Policies
Net revenues	70,469		127,781
Patient Care | Medicare | Before adoption of ASC 606
Summary of Significant Accounting Policies
Net revenues		65,737		120,872
Patient Care | Medicaid
Summary of Significant Accounting Policies
Net revenues	33,648		63,400
Patient Care | Medicaid | Before adoption of ASC 606
Summary of Significant Accounting Policies
Net revenues		34,788		62,964
Patient Care | Commercial Insurance/Managed Care (excluding Medicare and Medicaid Managed Care)
Summary of Significant Accounting Policies
Net revenues	77,621		148,432
Patient Care | Commercial Insurance/Managed Care (excluding Medicare and Medicaid Managed Care) | Before adoption of ASC 606
Summary of Significant Accounting Policies
Net revenues		80,631		155,053
Patient Care | Veterans Administration
Summary of Significant Accounting Policies
Net revenues	20,904		37,547
Patient Care | Veterans Administration | Before adoption of ASC 606
Summary of Significant Accounting Policies
Net revenues		18,814		34,340
Patient Care | Private Pay
Summary of Significant Accounting Policies
Net revenues	15,516		29,505
Patient Care | Private Pay | Before adoption of ASC 606
Summary of Significant Accounting Policies
Net revenues		16,251		30,629
Products & Services
Summary of Significant Accounting Policies
Net revenues	98,643	92,334	$ 186,653	179,578
Products & Services | Minimum
Summary of Significant Accounting Policies
Payment terms			30 days
Products & Services | Maximum
Summary of Significant Accounting Policies
Payment terms			90 days
Products & Services | Operating segments
Summary of Significant Accounting Policies
Net revenues	48,808	47,165	$ 94,296	93,209
Products & Services | Before adoption of ASC 606 | Operating segments
Summary of Significant Accounting Policies
Net revenues		47,165		93,209
Products & Services | Distribution, net of intersegment revenue eliminations | Operating segments
Summary of Significant Accounting Policies
Net revenues	34,684		66,035
Products & Services | Distribution, net of intersegment revenue eliminations | Before adoption of ASC 606 | Operating segments
Summary of Significant Accounting Policies
Net revenues		31,967		62,590
Products & Services | Therapeutic solutions | Operating segments
Summary of Significant Accounting Policies
Net revenues	$ 14,124		$ 28,261
Products & Services | Therapeutic solutions | Before adoption of ASC 606 | Operating segments
Summary of Significant Accounting Policies
Net revenues		$ 15,198		$ 30,619