Investments (Available for sale equity investments) (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Mar. 31, 2023
Marketable Securities [Abstract]
Amortized cost, equity investments	$ 54,757	$ 55,631
Estimated market value, equity investments	62,286	61,357
Common stocks [Member]
Marketable Securities [Abstract]
Amortized cost, equity investments	29,613	29,577
Estimated market value, equity investments	41,730	39,375
Non-redeemable preferred stocks [Member]
Marketable Securities [Abstract]
Amortized cost, equity investments	25,144	26,054
Estimated market value, equity investments	$ 20,556	$ 21,982