Investments (Available for sale equity investments) (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Marketable Securities [Abstract]
Amortized cost, equity investments	$ 17,226	$ 17,574
Estimated market value, equity investments	27,489	24,168
Common stocks [Member]
Marketable Securities [Abstract]
Amortized cost, equity investments	9,775	10,123
Estimated market value, equity investments	19,988	17,379
Non-redeemable preferred stocks [Member]
Marketable Securities [Abstract]
Amortized cost, equity investments	7,451	7,451
Estimated market value, equity investments	$ 7,501	$ 6,789