SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Accounts Receivable Aging (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross accounts receivable	$ 88,185	$ 123,434
Allowance for doubtful accounts	0	(37,912)
Net accounts receivable	88,185	85,522
Government
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross accounts receivable	19,971	30,684
Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross accounts receivable	63,580	82,546
Patient
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross accounts receivable	4,634	10,204
Receivables 0 to 180 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross accounts receivable	83,747	86,946
Receivables 0 to 180 Days Past Due | Government
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross accounts receivable	18,367	20,602
Receivables 0 to 180 Days Past Due | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross accounts receivable	61,561	63,767
Receivables 0 to 180 Days Past Due | Patient
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross accounts receivable	3,819	2,577
Receivables Over 180 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross accounts receivable	4,438	36,488
Receivables Over 180 Days Past Due | Government
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross accounts receivable	1,604	10,082
Receivables Over 180 Days Past Due | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross accounts receivable	2,019	18,779
Receivables Over 180 Days Past Due | Patient
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross accounts receivable	$ 815	$ 7,627