STOCK-BASED COMPENSATION - COMPENSATION EXPENSE (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016
Stock-based compensation expense
Stock-based compensation expense	$ 116,349	$ 81,879	$ 69,996
Capitalized stock-based compensation expense	90,914	74,717	30,367
Cost of goods sold
Stock-based compensation expense
Stock-based compensation expense	24,610	21,056	15,323
Selling and marketing
Stock-based compensation expense
Stock-based compensation expense	13,258	9,963	9,425
General and administrative
Stock-based compensation expense
Stock-based compensation expense	58,037	42,908	40,322
Research and development
Stock-based compensation expense
Stock-based compensation expense	18,020	7,952	4,926
Business reorganization
Stock-based compensation expense
Stock-based compensation expense	$ 2,424	$ 0	$ 0