EMPLOYEE BENEFIT PLANS - Net Periodic Pension Cost (Credit) (Details) - United Kingdom - Pension Plan - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 322	$ 443	$ 970	$ 1,310
Expected return on plan assets	(504)	(580)	(1,515)	(1,715)
Amortization of prior service cost	9	8	26	24
Net periodic pension credit	$ (173)	$ (129)	$ (519)	$ (381)