SCHEDULE II VALUATION AND QUALIFYING ACCOUNTS (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Allowance for Doubtful Accounts
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance Beginning of Period	$ 15,046	$ 15,194	$ 13,476
Additions Charged to Operating Expense	7,901	6,907	4,793
Deductions from Reserves	6,774	7,055	3,075
Balance End of Period	16,173	15,046	15,194
Revenue Allowance
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance Beginning of Period	14,203	16,232	12,185
Additions Charged to Operating Expense	24,862	24,252	28,312
Deductions from Reserves	27,439	26,281	24,265
Balance End of Period	11,626	14,203	16,232
Valuation Allowance on Deferred Tax Assets
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance Beginning of Period	55,189	30,916	29,061
Additions Charged to Operating Expense	9,052	22,564	2,274
Deductions from Reserves	4,114	1,709	(419)
Balance End of Period	$ 68,355	$ 55,189	$ 30,916