Investments (Available for sale equity investments) (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Mar. 31, 2024
Debt Securities Trading And Equity Securities FvNi Cost [Abstract]
Amortized cost, equity investments	$ 54,566	$ 54,748
Estimated market value, equity investments	63,295	66,274
Common Stock [Member]
Debt Securities Trading And Equity Securities FvNi Cost [Abstract]
Amortized cost, equity investments	29,422	29,604
Estimated market value, equity investments	41,529	45,014
Nonredeemable Preferred Stock [Member]
Debt Securities Trading And Equity Securities FvNi Cost [Abstract]
Amortized cost, equity investments	25,144	25,144
Estimated market value, equity investments	$ 21,766	$ 21,260