Description of Business and Liquidity (Details) $ in Thousands	3 Months Ended				6 Months Ended
	Sep. 30, 2023 USD ($)	Jun. 30, 2023 USD ($)	Sep. 30, 2022 USD ($)	Jun. 30, 2022 USD ($)	Sep. 30, 2023 USD ($) Segment	Sep. 30, 2022 USD ($)	Mar. 31, 2023 USD ($)
Description of Business [Abstract]
Number of operating segment | Segment					1
Number of reporting segment | Segment					1
Liquidity [Abstract]
Cash and cash equivalents	$ 1,408,231				$ 1,408,231		$ 1,676,813
Accumulated deficit	(4,368,897)				(4,368,897)		$ (3,772,754)
Net loss	$ (331,118)	$ (327,845)	$ (315,921)	$ (353,784)	$ (658,963)	$ (669,705)