REVENUE - RECEIVABLES AND CONTRACT LIABILITIES BALANCES (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2021 USD ($)
Contract with Customer, Asset [Roll Forward]
Beginning of period, January 1, 2021	$ 111,871
End of period, September 30, 2021	115,298
Increase in contract receivables during the period	3,427
Contract with Customer, Liability [Roll Forward]
Beginning of period, January 1, 2021	2,060
End of period, September 30, 2021	3,298
Increase in contract liabilities during the period	$ 1,238