Investments (Gain (Loss) on Marketable Equity Securities) (Details 2) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Investments [Abstract]
Gain (loss) on marketable equity securities, net	$ 24,066	$ (14,102)
Less: Net (gains) losses in earnings from marketable equity securities sold and donated	(2,982)	2,611
Net unrealized gains (losses) in earnings from marketable equity securities still held at the end of the period	$ 21,084	$ (11,491)

Amount of unrealized and realized 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

+ Details

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

- Definition

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

+ References

+ Details

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

- Definition

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).

+ References

+ Details

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

- References

No definition available.

+ Details

Name:	us-gaap_InvestmentsAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration