Investments (Available for sale equity investments) (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Mar. 31, 2022
Debt Securities Trading And Equity Securities FvNi Cost [Abstract]
Amortized cost, equity investments	$ 55,740	$ 53,728
Estimated market value, equity investments	59,673	72,307
Common Stock [Member]
Debt Securities Trading And Equity Securities FvNi Cost [Abstract]
Amortized cost, equity investments	29,686	27,674
Estimated market value, equity investments	37,619	46,212
Nonredeemable Preferred Stock [Member]
Debt Securities Trading And Equity Securities FvNi Cost [Abstract]
Amortized cost, equity investments	26,054	26,054
Estimated market value, equity investments	$ 22,054	$ 26,095