Investments Marketable Equity Securities Gains (Losses) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Marketable Equity Securities Gains (Losses) [Abstract]
Marketable equity securities (losses) gains, net	$ (967)	$ 3,854	$ 13,505	$ 9,265
Less net gains recognized on marketable equity securities sold	714	946	3,029	1,181
Unrealized (losses) gains recognized on marketable equity securities held	$ (1,681)	$ 2,908	$ 10,476	$ 8,084