Investments Marketable Equity Securities Gains (Losses) (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Marketable Equity Securities Gains (Losses) [Abstract]
Marketable equity securities (losses) gains, net	$ (2,701)	$ (967)	$ 10,461	$ 13,505
Less net gains recognized on marketable equity securities sold	2,568	714	39,884	3,029
Unrealized gains (losses) recognized on marketable equity securities held	$ (5,269)	$ (1,681)	$ (29,423)	$ 10,476

Amount of unrealized gain (loss) on investment in marketable security.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(7)(c))
-URI http://asc.fasb.org/extlink&oid=116634182&loc=SL114868664-224227

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration