Investments (Available for sale equity investments) (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Mar. 31, 2018
Marketable Securities [Abstract]
Amortized cost, equity investments	$ 17,574	$ 24,223
Estimated market value, equity investments	24,168	36,476
Common stocks [Member]
Marketable Securities [Abstract]
Amortized cost, equity investments	10,123	15,732
Estimated market value, equity investments	17,379	27,862
Non-redeemable preferred stocks [Member]
Marketable Securities [Abstract]
Amortized cost, equity investments	7,451	8,491
Estimated market value, equity investments	$ 6,789	$ 8,614