Equity Method Investments, Investment in Arbutus (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Mar. 31, 2023
Investments [Abstract]
Number of shares acquired (in shares)	800,792,365		800,792,365		760,143,393
Aggregate fair value investment	$ 250,393		$ 250,393		$ 304,317
Arbutus Biopharma Corporation [Member]
Investments [Abstract]
Equity method investment ownership percentage	23.00%		23.00%
Aggregate fair value investment	$ 78,900		$ 78,900		$ 117,700
Unrealized gain (losses) on investments	$ (10,500)	$ (31,100)	$ (38,800)	$ (41,600)
Closing price of common stock (in dollars per share)	$ 2.03		$ 2.03		$ 3.03
Arbutus Biopharma Corporation [Member] | Common Stock [Member]
Investments [Abstract]
Number of shares acquired (in shares)	38,847,462		38,847,462