Investments (Available for sale equity investments) (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Sep. 30, 2019
Marketable Securities [Abstract]
Amortized cost, equity investments	$ 27,962	$ 14,851
Estimated market value, equity investments	36,183	25,125
Common stocks [Member]
Marketable Securities [Abstract]
Amortized cost, equity investments	9,775	9,775
Estimated market value, equity investments	17,927	20,015
Non-redeemable preferred stocks [Member]
Marketable Securities [Abstract]
Amortized cost, equity investments	18,187	5,076
Estimated market value, equity investments	$ 18,256	$ 5,110