STOCK-BASED COMPENSATION - COMPENSATION EXPENSE (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Stock-based compensation expense
Stock-based compensation expense before income taxes	$ 247,700	$ 116,349	$ 81,879
Income tax benefit	(48,383)	(3,561)	(1,552)
Stock-based compensation expense, net of income tax benefit	199,317	112,788	80,327
Capitalized stock-based compensation expense	75,725	90,914	74,717
Cost of goods sold
Stock-based compensation expense
Stock-based compensation expense before income taxes	149,075	24,610	21,056
Selling and marketing
Stock-based compensation expense
Stock-based compensation expense before income taxes	23,685	13,258	9,963
General and administrative
Stock-based compensation expense
Stock-based compensation expense before income taxes	51,903	58,037	42,908
Research and development
Stock-based compensation expense
Stock-based compensation expense before income taxes	23,037	18,020	7,952
Business reorganization
Stock-based compensation expense
Stock-based compensation expense before income taxes	$ 0	$ 2,424	$ 0