SEGMENT INFORMATION - Revenue and Long-Lived Assets by Geographic Areas (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Revenue and Long-lived Assets by Geography
Revenue:	$ 375,061	$ 343,896	$ 718,711	$ 647,339
Long-lived assets (excluding goodwill, intangible assets and ROU assets):	104,261		104,261		$ 103,361
United States
Revenue and Long-lived Assets by Geography
Revenue:	354,000	320,701	673,821	599,179
Long-lived assets (excluding goodwill, intangible assets and ROU assets):	95,173		95,173		95,822
All other countries
Revenue and Long-lived Assets by Geography
Revenue:	21,061	$ 23,195	44,890	$ 48,160
Long-lived assets (excluding goodwill, intangible assets and ROU assets):	$ 9,088		$ 9,088		$ 7,539