Investments Marketable Equity Securities Gains (Losses) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Marketable Equity Securities Gains (Losses) [Abstract]
Marketable equity securities gains, net	$ 64,570	$ 3,144	$ 13,162	$ 14,472
Less net gains recognized on marketable equity securities sold	36,993	2,271	37,316	2,315
Unrealized gains (losses) recognized on marketable equity securities held	$ 27,577	$ 873	$ (24,154)	$ 12,157