Fair Value Measurements - Reconciliation of Changes in the Fair Value of Embedded Derivatives (Details) $ in Thousands	12 Months Ended
Dec. 31, 2016 USD ($)
Embedded Derivative [Abstract]
Issuance of First Lien Notes and Second Lien Notes	$ 47,618
Change in fair value	2,505
End of period	$ 50,123

Embedded derivative issuance of first lien notes and second lien notes.

No definition available.

Name:	cie_EmbeddedDerivativeIssuanceOfFirstLienNotesAndSecondLienNotes
Namespace Prefix:	cie_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- References

No definition available.

+ Details

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Fair value as of the balance sheet date of the embedded derivative or group of embedded derivatives classified as a liability.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4B
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=64837297&loc=SL5624163-113959

+ Details

Name:	us-gaap_EmbeddedDerivativeFairValueOfEmbeddedDerivativeLiability
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Net Increase or Decrease in the fair value of the embedded derivative or group of embedded derivatives included in earnings in the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-URI http://asc.fasb.org/extlink&oid=64837297&loc=SL5624171-113959

+ Details

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Data Type:	xbrli:monetaryItemType
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Period Type:	duration