SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Allowances for credit loss rollforward (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Accounts Receivable, Allowance for Credit Loss
Balance at beginning of year	$ 9,255	$ 5,738
Provisions for losses and sales adjustments - accounts receivable	2,831	3,517	$ 1,636
Collections of accounts previously written off	0	0
Balance at end of year	$ 12,086	$ 9,255	$ 5,738