Condensed Consolidated Statement of Shareholders' Equity - 9 months ended Dec. 31, 2016 - USD ($) $ in Thousands	Total	Common Shares	Common Shares Subscribed	Additional Paid in Capital	Accumulated Deficit
Beginning balance (in shares) at Mar. 31, 2016	37,231,342	37,231,342
Beginning balance at Mar. 31, 2016	$ (223)	$ 1	$ (1)	$ 1,434	$ (1,657)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Sale of common shares in initial public offering ($15.00 per share), net of underwriting discounts and commissions and offering expenses of $17,536 (in shares)		14,500,000
Sale of common shares in initial public offering ($15.00 per share), net of underwriting discounts and commissions and offering expenses of $17,536	199,964	$ 0		199,964
Shares issued to Takeda under the Takeda license agreement (in shares)		5,077,001
Shares issued to Takeda under the Takeda license agreement	$ 7,740	$ 0		7,740
Shares issued to settle the warrant liability to Takeda (in shares)	2,313,529	2,313,529
Shares issued to settle the warrant liability to Takeda	$ 32,537	$ 0		32,537
Share-based compensation expense (in shares)		1,128,222
Share-based compensation expense	2,223	$ 0		2,223
Capital contribution — share-based compensation	4,558			4,558
Capital contribution	1,035			1,035
Net loss	$ (61,766)				(61,766)
Ending balance (in shares) at Dec. 31, 2016	60,250,094	60,250,094
Ending balance at Dec. 31, 2016	$ 186,068	$ 1	$ (1)	$ 249,491	$ (63,423)