GOODWILL AND OTHER INTANGIBLE ASSETS - Schedule of Amortizable Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Goodwill and Other Intangible Assets [Line Items]
Cost	$ 133,299		$ 133,344
Accumulated Amortization	(114,610)		(113,627)
Net Book Value	18,689		19,717
Client-related
Goodwill and Other Intangible Assets [Line Items]
Cost	63,096		63,140
Accumulated Amortization	(54,703)		(54,368)
Net Book Value	$ 8,393		8,772
Client-related | Minimum
Goodwill and Other Intangible Assets [Line Items]
Useful Lives	4 years	4 years
Client-related | Maximum
Goodwill and Other Intangible Assets [Line Items]
Useful Lives	10 years	10 years
Technology
Goodwill and Other Intangible Assets [Line Items]
Cost	$ 64,842		64,843
Accumulated Amortization	(54,546)		(53,898)
Net Book Value	$ 10,296		10,945
Technology | Minimum
Goodwill and Other Intangible Assets [Line Items]
Useful Lives	2 years	2 years
Technology | Maximum
Goodwill and Other Intangible Assets [Line Items]
Useful Lives	10 years	10 years
Other
Goodwill and Other Intangible Assets [Line Items]
Cost	$ 5,361		5,361
Accumulated Amortization	(5,361)		(5,361)
Net Book Value	$ 0		$ 0
Other | Minimum
Goodwill and Other Intangible Assets [Line Items]
Useful Lives	1 year	1 year
Other | Maximum
Goodwill and Other Intangible Assets [Line Items]
Useful Lives	5 years	5 years