Rate of conversion of convertible common stock.

No definition available.

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Namespace Prefix:	ema_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The price per share of the conversion of the debt instrument to common shares.

+ References

No definition available.

+ Details

Name:	ema_DebtInstrumentConvertibleConversionPerShare
Namespace Prefix:	ema_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage used to convert debt into common shares.

+ References

No definition available.

+ Details

Name:	ema_DebtInstrumentConvertibleConversionPercent
Namespace Prefix:	ema_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage of convertible debentures converted into common stock

+ References

No definition available.

+ Details

Name:	ema_PercentageOfConvertibleDebenturesConvertedIntoCommonStock
Namespace Prefix:	ema_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Total number of common shares of an entity that have been sold or granted to shareholders (includes common shares that were issued, repurchased and remain in the treasury). These shares represent capital invested by the firm's shareholders and owners, and may be all or only a portion of the number of shares authorized. Shares issued include shares outstanding and shares held in the treasury.

+ 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(29))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_CommonStockSharesIssued
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Threshold number of specified trading days that common stock price to conversion price of convertible debt instruments must exceed threshold percentage within a specified consecutive trading period to trigger conversion feature.

+ References

No definition available.

+ Details

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

- Definition

Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

+ 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)(2))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentMaturityDate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

The cash inflow from an obligation which places a lender in a lien position behind debt having a higher priority of repayment (senior loan) in liquidation of the entity's assets scheduled to be repaid within one year or in the normal operating cycle of the entity, if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3255-108585

+ Details

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

- Definition

Stated interest rate of the subordinated debt.

+ References

No definition available.

+ Details

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

- Details

Name:	dei_LegalEntityAxis=us-gaap_ParentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	us-gaap_BusinessAcquisitionAxis=ema_TecoEnergyIncMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Common Stock (Narrative) (Details) - Emera Inc - Convertible Subordinated Debt [Member] $ / shares in Units, shares in Thousands, $ in Millions			12 Months Ended
	Aug. 02, 2016	Sep. 28, 2015 CAD ($) $ / shares	Dec. 31, 2017 NumberOfDays shares
Debt Instrument [Line Items]
Debt Instrument, Maturity Date	Sep. 29, 2025
Convertible debenture interest rate	0.00%
Common Stock, Shares, Issued \| shares			52,140
Common Stock, Conversion Rate			95.00%
Debt Instrument, Convertible, Threshold Trading Days \| NumberOfDays			20
Debentures Converted (%)			99.90%
TECO Energy Inc [Member]
Debt Instrument [Line Items]
Debt Instrument, Convertible, Conversion Percent		4.00%
Aggregate proceeds of the Debenture Offering \| $		$ 2,185
Debt Instrument, Convertible, Conversion Per Share \| $ / shares		$ 1,000