Financial Instruments and Investments Transfers Between Levels (Details) - USD ($)	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Fair Value Disclosures [Abstract]
Fair Value, Assets, Level 1 to Level 2 Transfers, Description	no	no
Fair Value, Assets, Level 2 to Level 1 Transfers, Description	no	no
Fair Value, Assets, Level 3 Purchases, (Sales), Issuances, (Settlements)	$ 0	$ 0

Description of the transfers of assets measured on a recurring basis out of Level 1 and into Level 2 of the fair value hierarchy.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bb)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

+ Details

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Balance Type:	na
Period Type:	duration

- Definition

Description of the transfers of assets measured on a recurring basis out of Level 2 and into Level 1 of the fair value hierarchy.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
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- References

No definition available.

+ Details

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- Definition

Amount of purchases, (sales), issuances and (settlements) of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

+ Details

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