Investments (Available for sale equity investments) (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Mar. 31, 2020
Marketable Securities [Abstract]
Amortized cost, equity investments	$ 29,809	$ 14,851
Estimated market value, equity investments	42,117	25,125
Common stocks [Member]
Marketable Securities [Abstract]
Amortized cost, equity investments	9,775	9,775
Estimated market value, equity investments	20,440	20,015
Non-redeemable preferred stocks [Member]
Marketable Securities [Abstract]
Amortized cost, equity investments	20,034	5,076
Estimated market value, equity investments	$ 21,677	$ 5,110