Investments Marketable Equity Securities Gains (Losses) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Marketable Equity Securities Gains (Losses) [Abstract]
Marketable equity securities gain (loss), net	$ 3,144	$ 4,440	$ 14,472	$ 5,411
Net gains (losses) recognized on marketable equity securities sold	2,271	139	2,315	235
Unrealized gains (losses) recognized on marketable equity securities held	$ 873	$ 4,301	$ 12,157	$ 5,176