Stock-Based Compensation - Stock Based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2015	Dec. 31, 2014
Summary of Stock-Based Compensation Expense of Stock Options and Restricted Stock Units
Stock-based compensation expense	$ 6,152	$ 4,882	$ 18,195	$ 14,308
Stock-based compensation capitalized to inventory	(11)	(25)	(28)	(5)
Total	6,141	4,857	18,167	14,303
Cost of Revenues
Summary of Stock-Based Compensation Expense of Stock Options and Restricted Stock Units
Stock-based compensation expense	151	97	377	226
Research and Development Expense
Summary of Stock-Based Compensation Expense of Stock Options and Restricted Stock Units
Stock-based compensation expense	4,500	2,992	12,515	9,039
Selling, General and Administrative
Summary of Stock-Based Compensation Expense of Stock Options and Restricted Stock Units
Stock-based compensation expense	1,501	1,793	5,303	5,043
Outstanding stock options
Summary of Stock-Based Compensation Expense of Stock Options and Restricted Stock Units
Stock-based compensation expense	352	454	848	1,160
Outstanding RSUs
Summary of Stock-Based Compensation Expense of Stock Options and Restricted Stock Units
Stock-based compensation expense	$ 5,800	$ 4,428	$ 17,347	$ 13,148