GOODWILL AND INTANGIBLE ASSETS - Schedule of intangible assets with definite lives (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Intangible assets with definite lives
Cost	$ 225,200	$ 225,400
Accumulated Amortization	(129,462)	(107,040)
Total intangible assets with definite lives, net	95,738	118,360
Technology
Intangible assets with definite lives
Cost	87,700	87,700
Accumulated Amortization	(58,768)	(48,166)
Total intangible assets with definite lives, net	28,932	39,534
Customer lists
Intangible assets with definite lives
Cost	77,300	77,300
Accumulated Amortization	(21,614)	(18,560)
Total intangible assets with definite lives, net	55,686	58,740
Trademarks and tradenames
Intangible assets with definite lives
Cost	17,000	17,200
Accumulated Amortization	(11,513)	(9,947)
Total intangible assets with definite lives, net	5,487	7,253
Website content
Intangible assets with definite lives
Cost	43,200	43,200
Accumulated Amortization	(37,567)	(30,367)
Total intangible assets with definite lives, net	$ 5,633	$ 12,833