Shareholders' Equity	6 Months Ended
Sep. 30, 2018
Equity [Abstract]
Shareholders' Equity	Shareholders’ Equity (A) Underwritten Secondary Public Equity Offering of Common Stock In July 2018, the Company completed an underwritten secondary public equity offering of 3,333,334 of its common shares at a public offering price of $22.50 per common share. Subsequently, in August 2018, the Company issued and sold an additional 200,065 common shares upon the partial exercise of the underwriters’ over-allotment option at a price of $22.50 per common share. After deducting the underwriting discounts and commissions and estimated offering costs payable by the Company, the net proceeds to the Company in connection with the underwritten secondary public equity offering, including the over-allotment option, were approximately $74.4 million. (B) Private Placement with RSL On April 2, 2018, the Company entered into a share purchase agreement, or the Purchase Agreement, with RSL, its controlling shareholder, pursuant to which the Company agreed to issue and sell to RSL 1,110,015 of its common shares at a purchase price of $20.27 per common share in a private placement, or the Private Placement. In April 2018, the Company received proceeds of $22.5 million from RSL at the closing of the Private Placement. (C) At-the-Market Equity Offering Program On April 2, 2018, the Company entered into a sales agreement, or the Sales Agreement, with Cowen and Company, LLC, or Cowen, to sell its common shares having an aggregate offering price of up to $100.0 million from time to time through an “at-the-market” equity offering program under which Cowen acts as the Company’s agent. During the three and six months ended September 30, 2018, the Company issued and sold none and 2,767,129, respectively, of its common shares under the Sales Agreement. The common shares were sold at a weighted-average price of $21.47 per common share for aggregate net proceeds to the Company of approximately $57.3 million, after deducting underwriting commissions and offering costs payable by the Company. The Company currently has approximately $40.6 million of capacity available under its “at-the-market” equity offering program. (D) Takeda Warrant Liability During the year ended March 31, 2018, the Company issued 4,432 common shares to Takeda pursuant to a warrant which expired on April 30, 2017.

Shareholders’ Equity

(A) Underwritten Secondary Public Equity Offering of Common Stock

In July 2018, the Company completed an underwritten secondary public equity offering of 3,333,334 of its common shares at a public offering price of $22.50 per common share. Subsequently, in August 2018, the Company issued and sold an additional 200,065 common shares upon the partial exercise of the underwriters’ over-allotment option at a price of $22.50 per common share. After deducting the underwriting discounts and commissions and estimated offering costs payable by the Company, the net proceeds to the Company in connection with the underwritten secondary public equity offering, including the over-allotment option, were approximately $74.4 million.

(B) Private Placement with RSL

On April 2, 2018, the Company entered into a share purchase agreement, or the Purchase Agreement, with RSL, its controlling shareholder, pursuant to which the Company agreed to issue and sell to RSL 1,110,015 of its common shares at a purchase price of $20.27 per common share in a private placement, or the Private Placement. In April 2018, the Company received proceeds of $22.5 million from RSL at the closing of the Private Placement.

On April 2, 2018, the Company entered into a sales agreement, or the Sales Agreement, with Cowen and Company, LLC, or Cowen, to sell its common shares having an aggregate offering price of up to $100.0 million from time to time through an “at-the-market” equity offering program under which Cowen acts as the Company’s agent. During the three and six months ended September 30, 2018, the Company issued and sold none and 2,767,129, respectively, of its common shares under the Sales Agreement. The common shares were sold at a weighted-average price of $21.47 per common share for aggregate net proceeds to the Company of approximately $57.3 million, after deducting underwriting commissions and offering costs payable by the Company. The Company currently has approximately $40.6 million of capacity available under its “at-the-market” equity offering program.

(D) Takeda Warrant Liability

During the year ended March 31, 2018, the Company issued 4,432 common shares to Takeda pursuant to a warrant which expired on April 30, 2017.