Debt Instrument, Covenant Compliance, Loan Limit Percentage

No definition available.

Name:	egn_DebtInstrumentCovenantComplianceLoanLimitPercentage
Namespace Prefix:	egn_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Debt to EBITDAX Ratio Maximum

+ References

No definition available.

+ Details

Name:	egn_DebtInstrumentCovenantComplianceMaximumDebtToEarningsBeforeInterestExpenseIncomeTaxesDepreciationDepletionAmortizationAndExplorationExpensesRatio
Namespace Prefix:	egn_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- Definition

Debt Instrument, Covenant Compliance, Minimum Current Assets To Current Liabilities, Ratio

+ References

No definition available.

+ Details

Name:	egn_DebtInstrumentCovenantComplianceMinimumCurrentAssetsToCurrentLiabilitiesRatio
Namespace Prefix:	egn_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- Definition

Debt Instrument, Cross Default Provision, Minimum Threshold Amount

+ References

No definition available.

+ Details

Name:	egn_DebtInstrumentCrossDefaultProvisionMinimumThresholdAmount
Namespace Prefix:	egn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Line of Credit, Cross Default Provision, Minimum Threshold Amount

+ References

No definition available.

+ Details

Name:	egn_LineOfCreditCrossDefaultProvisionMinimumThresholdAmount
Namespace Prefix:	egn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

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

- Definition

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

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

- Definition

Amount of current borrowing capacity under the credit facility considering any current restrictions on the amount that could be borrowed (for example, borrowings may be limited by the amount of current assets), but without considering any amounts currently outstanding under the facility.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_NotesPayableOtherPayablesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=egn_NotesPayable4625PercentDueSeptember12021Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_RevolvingCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LineOfCreditFacilityAxis=egn_SyndicatedCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=egn_CreditFacilitySeptember22014Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Long-Term Debt - Additional Information (Details) - USD ($)	Sep. 02, 2014	Apr. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Nov. 09, 2017
Debt Instrument [Line Items]
Cross default provision, threshold amount			$ 10,000,000
Initial borrowing base			1,050,000,000	$ 1,050,000,000
Credit facility cross default provision, threshold amount (more than)			$ 75,000,000
Notes \| 4.625% Notes, due September 1, 2021
Debt Instrument [Line Items]
Stated interest rate			4.625%
Credit facility
Debt Instrument [Line Items]
Initial borrowing base			$ 1,050,000,000
Syndicated Credit Facility \| Credit Facility, September 2, 2014
Debt Instrument [Line Items]
Term of credit facility	5 years
Debt covenant, debt to EBITDAX ratio (less than or equal to)			4.0
Debt covenant, current assets to current liabilities ratio (greater than or equal to)			1.0
Loan limit percentage (less than)			10.00%
Syndicated Credit Facility \| Credit facility
Debt Instrument [Line Items]
Maximum borrowing capacity					$ 1,700,000,000
Subsequent Event \| Syndicated Credit Facility \| Credit facility
Debt Instrument [Line Items]
Maximum borrowing capacity		$ 2,150,000,000
Initial borrowing base		$ 1,250,000,000