Ordinary and Preference Shares - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions			3 Months Ended		4 Months Ended	9 Months Ended
	Dec. 11, 2018	Aug. 03, 2018	Dec. 31, 2018	Dec. 31, 2017	Jul. 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Mar. 31, 2018
Class Of Stock [Line Items]
Common stock, shares issued			64,972,552			64,972,552		45,646,424
Ordinary Shares [Member]
Class Of Stock [Line Items]
Number of warrants exercised					8,414,683
Issuance of shares					8,414,683
Exercised price of warrants					$ 5.80
Proceeds from warrants exercise					$ 48.8
Common stock, shares issued			64,972,552			64,972,552		45,646,424
Share price			$ 6.12			$ 6.12
Proceeds from issuance of ordinary shares	$ 69.0
Newly issued ordinary shares Issues	10,615,385		10,615,385	7,864,683		19,085,068	15,914,683
Newly issued ordinary price per share	$ 6.50
Chief Executive Officer and Chairman | Ordinary Shares [Member]
Class Of Stock [Line Items]
Common stock, shares issued		55,000
Share price		$ 7.54
Proceeds from issuance of ordinary shares		$ 0.4