PROPERTY, PLANT AND EQUIPMENT - Long-Lived Assets by Geographical Area (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets, excluding intangible assets	$ 228,096	$ 216,859
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets, excluding intangible assets	187,719	178,895
Foreign Countries
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets, excluding intangible assets	$ 40,377	$ 37,964