REVENUE - Contract Asset and Liability (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Revenue from Contract with Customer [Abstract]
Receivables from contracts with customers	$ 201,400		$ 201,400		$ 199,300
Contract Assets:
Beginning balance			16,989	$ 13,999
Additions			20,292	23,818
Transfers to accounts receivable			(16,890)	(13,875)
Ending balance	20,391	$ 23,942	20,391	23,942
Contract Liabilities:
Beginning balance			(26,999)	(15,778)
Additions			(35,667)	(16,035)
Transfers to revenues	1,800	800	14,206	7,427
Ending balance	$ (48,460)	$ (24,386)	$ (48,460)	$ (24,386)