STOCK BASED COMPENSATION PLANS - Employee Stock Purchase Plan (Details) - USD ($)	1 Months Ended	12 Months Ended
	May 31, 2018	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
STOCK-BASED COMPENSATION PLANS.
Common stock initially authorized for issuance under the ESPP, Shares	1,000,000
Maximum contribution from employees	$ 25,000
Shares of common stock purchased under the ESPP		11,413	7,888	3,758
Expense recorded related to ESPP		$ 0	$ 0	$ 0