SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES AND PRACTICES - Goodwill Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Goodwill [Line Items]
Goodwill impairment charge	$ 0	$ 0		$ 0	$ 191,788
Goodwill	90,604			90,604		$ 91,351
IHT
Goodwill [Line Items]
Goodwill impairment charge			$ 191,800
Goodwill	0			0		0
MS
Goodwill [Line Items]
Net assets	127,000			127,000
Goodwill	$ 56,200			$ 56,200		$ 56,620