Investments (Realized and Unrealized Gains/Losses on Marketable Equity Securities) (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Investments [Abstract]
Marketable equity securities gains (losses), net	$ 20,625	$ (7,610)	$ 0
Less net gains recognized on marketable equity securities sold	16,344	1,190
Unrealized (losses) gains recognized on marketable equity securities held	$ 4,281	$ (8,800)

Amount of unrealized gain (loss) on investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 321
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=84241550&loc=SL75117546-209714

Name:	us-gaap_EquitySecuritiesFvNiUnrealizedGainLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration