SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Allowance for Doubtful Accounts (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2015 USD ($) accounts_receivable	Dec. 31, 2014 USD ($)
Change in Estimate of the Collectability of Accounts Receivable
Decrease in allowance for doubtful accounts		$ 6,700
Allowance for doubtful accounts, percentage of accounts receivable	35.50%	33.50%
Number of primary overall types of accounts receivable | accounts_receivable	3
Gross accounts receivable	$ 168,054	$ 198,061
Allowance for doubtful accounts	(59,689)	(66,405)
Net accounts receivable	108,365	131,656
0-180 Days
Change in Estimate of the Collectability of Accounts Receivable
Gross accounts receivable	128,315	139,150
Over 180 Days
Change in Estimate of the Collectability of Accounts Receivable
Gross accounts receivable	39,739	58,911
Government
Change in Estimate of the Collectability of Accounts Receivable
Gross accounts receivable	31,313	38,848
Government | 0-180 Days
Change in Estimate of the Collectability of Accounts Receivable
Gross accounts receivable	19,944	25,812
Government | Over 180 Days
Change in Estimate of the Collectability of Accounts Receivable
Gross accounts receivable	11,369	13,036
Commercial
Change in Estimate of the Collectability of Accounts Receivable
Gross accounts receivable	125,702	143,752
Commercial | 0-180 Days
Change in Estimate of the Collectability of Accounts Receivable
Gross accounts receivable	103,357	108,439
Commercial | Over 180 Days
Change in Estimate of the Collectability of Accounts Receivable
Gross accounts receivable	22,345	35,313
Patient
Change in Estimate of the Collectability of Accounts Receivable
Gross accounts receivable	11,039	15,461
Patient | 0-180 Days
Change in Estimate of the Collectability of Accounts Receivable
Gross accounts receivable	5,014	4,899
Patient | Over 180 Days
Change in Estimate of the Collectability of Accounts Receivable
Gross accounts receivable	$ 6,025	$ 10,562