ACCOUNTS RECEIVABLE, NET - Allowance for Disallowed Revenue and Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Allowance for Disallowed Revenue
Balance at the beginning	$ 61,137	$ 81,306	$ 87,192
Additions	36,962	48,961	60,076
Reductions	(41,866)	(69,130)	(65,962)
Balance at the end	56,233	61,137	81,306
Allowance for Doubtful Accounts
Balance at the beginning	15,521	15,027	9,944
Additions	9,423	13,727	14,515
Reductions	(10,879)	(13,233)	(9,432)
Balance at the end	14,065	15,521	15,027
Dosteon | Income (loss) from discontinued operations, net of income taxes
Allowance for Doubtful Accounts
Bad debt expense	0	0	1,700
Disallowed revenue	$ 0	$ 0	$ (200)