SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Accounts Receivable Aging (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross accounts receivable	$ 96,917	$ 123,434
Allowance for doubtful accounts	0	(37,912)
Net accounts receivable	96,917	85,522
Government
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross accounts receivable	17,964	30,684
Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross accounts receivable	74,105	82,546
Patient
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross accounts receivable	4,848	10,204
Receivables 0 to 180 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross accounts receivable	88,145	86,946
Receivables 0 to 180 Days Past Due | Government
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross accounts receivable	15,772	20,602
Receivables 0 to 180 Days Past Due | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross accounts receivable	69,014	63,767
Receivables 0 to 180 Days Past Due | Patient
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross accounts receivable	3,359	2,577
Receivables Over 180 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross accounts receivable	8,772	36,488
Receivables Over 180 Days Past Due | Government
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross accounts receivable	2,192	10,082
Receivables Over 180 Days Past Due | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross accounts receivable	5,091	18,779
Receivables Over 180 Days Past Due | Patient
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross accounts receivable	$ 1,489	$ 7,627