Financial Instruments And Investments Unrealized gains and losses on equity securities (Details) $ in Thousands	3 Months Ended
Mar. 31, 2018 USD ($)
Unrealized Gains and losses recognized [Line Items]
Net gains and (losses) recognized on equity securities	$ (1,991)
Less: Net (gains) and losses recognized on equity securities sold	1,790
Unrealized gains and (losses) recognized on equity securities still held at reporting date	$ (3,781)

Amount of unrealized gain (loss) recognized in the income statement on unsold other securities.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3602-108585

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