INCOME TAXES - Unrecognized tax benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2019
Income Tax Disclosure [Abstract]
Balance at beginning of period	$ 23,400	$ 19,600	$ 15,415
Increases related to prior year tax positions	0	2,458	325
Decreases related to prior year tax positions	(139)	(1,048)	(292)
Increases related to current year tax positions	1,765	2,433	5,483
Increases related to current year tax positions	0	(43)	(1,331)
Balance at end of period	$ 25,026	$ 23,400	$ 19,600