SEGMENT AND GEOGRAPHICAL INFORMATION - Long-Lived Assets by Geographic Area (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets	$ 597,766	$ 481,209
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets	586,702	471,970
International
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets	$ 11,064	$ 9,239