GOODWILL AND OTHER INTANGIBLES - Schedule of Amortizable Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2022	Dec. 31, 2021
Goodwill and Other Intangible Assets [Line Items]
Cost	$ 135,645	$ 135,668
Accumulated Amortization	(122,554)	(121,605)
Total	13,091	14,063
Client-related
Goodwill and Other Intangible Assets [Line Items]
Cost	63,142	63,165
Accumulated Amortization	(57,662)	(57,342)
Total	5,480	5,823
Technology
Goodwill and Other Intangible Assets [Line Items]
Cost	67,142	67,142
Accumulated Amortization	(59,531)	(58,902)
Total	7,611	8,240
Other
Goodwill and Other Intangible Assets [Line Items]
Cost	5,361	5,361
Accumulated Amortization	(5,361)	(5,361)
Total	$ 0	$ 0
Minimum | Client-related
Goodwill and Other Intangible Assets [Line Items]
Useful Lives	4 years	4 years
Minimum | Technology
Goodwill and Other Intangible Assets [Line Items]
Useful Lives	2 years	2 years
Minimum | Other
Goodwill and Other Intangible Assets [Line Items]
Useful Lives	1 year	1 year
Maximum | Client-related
Goodwill and Other Intangible Assets [Line Items]
Useful Lives	10 years	10 years
Maximum | Technology
Goodwill and Other Intangible Assets [Line Items]
Useful Lives	10 years	10 years
Maximum | Other
Goodwill and Other Intangible Assets [Line Items]
Useful Lives	5 years	5 years