DESCRIPTION OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Revenue timing (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Revenue recognition		$ 216,136	$ 208,475	$ 206,547
Performance obligations satisfied in prior periods		9,900
Deferred revenue		87	80
Revenue recognized		100	300
Tripartite Agreement-Yescart
Revenue recognition	$ 11,200	11,200
Performance obligations transferred at a point in time [Member]
Revenue recognition		214,826	206,617	205,422
Performance obligations transferred over time [Member]
Revenue recognition		$ 1,310	$ 1,858	$ 1,125