Stockholders’ Equity (Details) - USD ($) $ / shares in Units, $ in Millions				1 Months Ended	6 Months Ended	12 Months Ended		14 Months Ended
	Dec. 20, 2019	Jul. 31, 2018	Sep. 22, 2017	Dec. 31, 2019	Jun. 30, 2019	Jan. 12, 2020	Dec. 31, 2019	Mar. 12, 2020	Jun. 25, 2019	Mar. 31, 2018
Public offering | Ordinary Shares
Stockholders' Equity
Number of shares issued		18,181,818	9,411,765
Shares issued, price per share		$ 2.75	$ 8.50
Gross proceeds from sale of stock		$ 50.0	$ 80.0
Net proceeds from sale of stock		$ 46.3	$ 73.3
Cantor Fitzgerald and Co. | At-the-market offering | Ordinary Shares
Stockholders' Equity
Number of shares issued					10,316,190
Gross proceeds from sale of stock					$ 37.8
Net proceeds from sale of stock					36.3
Value of shares unsold at termination date					$ 12.2
Maximum aggregate gross proceeds under the sales agreement										$ 50.0
Jefferies LLC | At-the-market offering
Stockholders' Equity
Gross proceeds from sale of stock							$ 14.4
Net proceeds from sale of stock							$ 13.6
Maximum aggregate gross proceeds under the sales agreement									$ 50.0
Jefferies LLC | At-the-market offering | Ordinary Shares
Stockholders' Equity
Number of shares issued							6,505,268
Purchasers | Purchase agreement
Stockholders' Equity
Number of shares issued	13,793,106			13,793,106
Number of ordinary shares that can be purchased by warrant holders	13,793,106			13,793,106			13,793,106
Share and warrant price	$ 1.45			$ 1.45
Per share exercise price of right	$ 1.90			$ 1.90			$ 1.90
Term	3 years			3 years			3 years
Gross proceeds from sale of stock	$ 20.1			$ 20.1
Estimate | Jefferies LLC | At-the-market offering | Maximum
Stockholders' Equity
Gross proceeds from sale of stock						$ 35.6		$ 35.6