Net Loss Per Share - Computation of Earnings Per Share Basic and Diluted (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2015
Numerator:
Net loss	$ (85,069)	$ (33,878)	$ (59,059)
Net loss available to ordinary shareholders - basic and diluted	$ (85,069)	$ (33,878)	$ (59,059)
Denominator:
Weighted-average shares outstanding - basic and diluted	28,145,472	19,558,152	14,773,386
Loss per share - basic and diluted	$ (3.02)	$ (1.73)	$ (4.00)