STOCK-BASED COMPENSATION - Stock Option Activity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Stock Option Rollforward
Stock options outstanding at the beginning of the period (in shares)	3,114	3,998
Options granted (in shares)	0	81
Options exercised (in shares)	(124)	(115)
Options canceled and forfeited (in shares)	(16)	(73)
Options outstanding at the end of the period (in shares)	2,974	3,891
Weighted-average fair value of grants during the period (in dollars per share)	$ 0	$ 8.57
Total intrinsic value of options exercised during the period	$ 1,402	$ 1,186
Weighted-average remaining recognition period at period-end (in years)	2 years 5 months 15 days	2 years 4 months 6 days
Stock Award Rollforward
Stock awards outstanding at the beginning of the period (in shares)	7,820	5,939
Stock awards granted (in shares)	1,147	948
Stock awards vested (in shares)	(329)	(299)
Stock awards canceled and forfeited (in shares)	(445)	(168)
Stock awards outstanding at the end of the period: (in shares)	8,193	6,420
Weighted-average fair value of grants during the period (in dollars per share)	$ 22.40	$ 22.20
Weighted-average remaining recognition period at period-end (in years)	2 years 1 month 9 days	2 years 4 months 24 days
Total unrecognized compensation expense at period-end	$ 109,422	$ 67,025