SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Allowance for Doubtful Accounts (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2016 USD ($) accounts_receivable	Dec. 31, 2015 USD ($)
Change in Estimate of the Collectability of Accounts Receivable
Allowance for doubtful accounts, percentage of accounts receivable	28.60%	38.00%
Number of primary overall types of accounts receivable | accounts_receivable	3
Gross accounts receivable	$ 156,541	$ 157,042
Allowance for doubtful accounts	(44,730)	(59,689)
Net accounts receivable	111,811	97,353
0 - 180 days
Change in Estimate of the Collectability of Accounts Receivable
Gross accounts receivable	121,590	119,435
Over 180 days
Change in Estimate of the Collectability of Accounts Receivable
Gross accounts receivable	34,951	37,607
Government
Change in Estimate of the Collectability of Accounts Receivable
Gross accounts receivable	28,169	31,313
Government | 0 - 180 days
Change in Estimate of the Collectability of Accounts Receivable
Gross accounts receivable	19,891	19,944
Government | Over 180 days
Change in Estimate of the Collectability of Accounts Receivable
Gross accounts receivable	8,278	11,369
Commercial
Change in Estimate of the Collectability of Accounts Receivable
Gross accounts receivable	117,592	114,690
Commercial | 0 - 180 days
Change in Estimate of the Collectability of Accounts Receivable
Gross accounts receivable	97,744	94,477
Commercial | Over 180 days
Change in Estimate of the Collectability of Accounts Receivable
Gross accounts receivable	19,848	20,213
Patient
Change in Estimate of the Collectability of Accounts Receivable
Gross accounts receivable	10,780	11,039
Patient | 0 - 180 days
Change in Estimate of the Collectability of Accounts Receivable
Gross accounts receivable	3,955	5,014
Patient | Over 180 days
Change in Estimate of the Collectability of Accounts Receivable
Gross accounts receivable	$ 6,825	$ 6,025