UNAUDITED SELECTED CONSOLIDATED QUARTERLY FINANCIAL DATA (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2019
Quarterly Financial Information Disclosure [Abstract]
Total revenue	$ 144,719	$ 136,685	$ 129,133	$ 121,807	$ 121,478	$ 118,567	$ 109,517	$ 96,675	$ 532,344	$ 446,237	$ 352,586
Gross profit	83,606	76,277	72,637	69,674	63,857	62,348	59,820	58,984
Loss from operations	(40,036)	(35,255)	(33,098)	(37,760)	(46,154)	(43,168)	(37,944)	(32,553)	(146,149)	(159,819)	(89,633)
Net loss	$ (45,034)	$ (40,225)	$ (38,413)	$ (41,913)	$ (50,100)	$ (47,071)	$ (40,932)	$ (34,265)	$ (165,585)	$ (172,368)	$ (88,739)
Net loss per share:
Basic and diluted (in dollars per share)	$ (0.42)	$ (0.38)	$ (0.37)	$ (0.40)	$ (0.49)	$ (0.47)	$ (0.42)	$ (0.36)	$ (1.57)	$ (1.72)	$ (0.94)