SHARE-BASED PAYMENTS - Schedule of Valuation Assumptions (Details) - $ / shares	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Compensation Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate			0.87%
Expected life	5 years	5 years	5 years
Expected volatility	63.00%		75.10%
Expected dividend yield	0.00%	0.00%	0.00%
Weighted Average Expected Life Of Option	5 years	5 years	4 years 11 months 27 days
Weighted-average expected life of option	5 years	5 years	5 years
Weighted-average grant date fair value (in dollars per share)	$ 1.20		$ 2.64
Business Combinations and Asset Acquisitions
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected dividend yield			0.00%
Weighted Average Expected Life Of Option			4 years 6 months 7 days
Weighted-average grant date fair value (in dollars per share)			$ 1.89
Minimum \| Compensation Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	1.93%	1.03%
Expected volatility		64.70%
Weighted-average grant date fair value (in dollars per share)		$ 1.22
Minimum \| Business Combinations and Asset Acquisitions
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate			0.00%
Expected life			18 days
Expected volatility			18.47%
Weighted-average expected life of option			18 days
Maximum \| Compensation Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate		1.43%
Expected volatility		74.80%
Weighted-average grant date fair value (in dollars per share)		$ 1.23
Maximum \| Business Combinations and Asset Acquisitions
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate			2.35%
Expected life			10 years
Expected volatility			93.31%
Weighted-average expected life of option			10 years

Weighted-average expected life of option

No definition available.

Name:	efr_WeightedAverageExpectedLifeOfOption
Namespace Prefix:	efr_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term.

+ References

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The estimated measure of the percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

+ References

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The risk-free interest rate assumption that is used in valuing an option on its own shares.

+ References

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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

- Definition

The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

+ References

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

Expected term of share-based compensation awards, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(i)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 14.D.2)
-URI http://asc.fasb.org/extlink&oid=27013229&loc=d3e301413-122809

+ Details

Name:	us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_PlanNameAxis=efr_CompensationPlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PlanNameAxis=efr_BusinessCombinationsandAssetAcquisitionsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: