ACCOUNTING POLICIES - Allowances (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Allowances
Allowance for credit losses on trade accounts receivable	$ 3,600	$ 1,800
Provision for losses on accounts receivable	4,327	$ 1,223	$ 2,336
Write-offs, net of recoveries	$ 2,500