Investments (Available for sale equity investments) (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Mar. 31, 2023
Debt Securities Trading And Equity Securities FvNi Cost [Abstract]
Amortized cost, equity investments	$ 54,746	$ 55,631
Estimated market value, equity investments	62,036	61,357
Common Stock [Member]
Debt Securities Trading And Equity Securities FvNi Cost [Abstract]
Amortized cost, equity investments	29,602	29,577
Estimated market value, equity investments	42,045	39,375
Nonredeemable Preferred Stock [Member]
Debt Securities Trading And Equity Securities FvNi Cost [Abstract]
Amortized cost, equity investments	25,144	26,054
Estimated market value, equity investments	$ 19,991	$ 21,982