REVENUE, DEFERRED REVENUE, AND REMAINING PERFORMANCE OBLIGATIONS - Sources of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Segment Reporting Information [Line Items]
Total revenue	$ 199,498	$ 144,952	$ 533,992	$ 426,929
Subscription revenue | Product Concentration Risk
Segment Reporting Information [Line Items]
Total revenue	185,643	137,446	507,281	401,264
Professional services revenue | Product Concentration Risk
Segment Reporting Information [Line Items]
Total revenue	$ 13,855	$ 7,506	$ 26,711	$ 25,665