XML 108 R93.htm IDEA: XBRL DOCUMENT
v3.6.0.2

Income Taxes (Reasonable Probablity of Tax Benefit) (Details) - CAD CAD in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2016 | Dec. 31, 2015
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued [Abstract] |  |
Accrued interest | CAD 1 | CAD 1
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items] |  |
Temporary Differences/Potential change | 667 | CAD 669
Settlement with Taxing Authority [Member] | 2006 through 2010 years [Member] | Nova Scotia Power Inc. [Member] | Canada Revenue Agency [Member] |  |
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items] |  |
Net amount in dispute | 62 |
Prepaid amount in dispute | CAD 23 |

X
- Definition Prepaid portion of estimated amount of loss resulting from an adverse tax position. + References No definition available. + Details
Name: | ema_IncomeTaxExaminationPrepaymentOfPossibleLoss
Namespace Prefix: | ema_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Estimated amount of loss resulting from an adverse tax position. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (d)(3) -URI http://asc.fasb.org/extlink&oid=65882285&loc=d3e32718-109319 + Details
Name: | us-gaap_IncomeTaxExaminationEstimateOfPossibleLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The amount of the unrecognized tax benefit of a position taken for which it is reasonably possible that the total amount thereof will significantly increase or decrease within twelve months of the balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=65882285&loc=d3e32718-109319 + Details
Name: | us-gaap_SignificantChangeInUnrecognizedTaxBenefitsIsReasonablyPossibleAmountOfUnrecordedBenefit
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- 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_SignificantChangeInUnrecognizedTaxBenefitsIsReasonablyPossibleLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccruedAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of interest expense accrued for an underpayment of income taxes. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=65882285&loc=d3e32718-109319 + Details
Name: | us-gaap_UnrecognizedTaxBenefitsInterestOnIncomeTaxesAccrued
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Details
Name: | us-gaap_ReasonablyPossibleSignificantChangeInUnrecognizedTaxBenefitsByItemAxis=us-gaap_SettlementWithTaxingAuthorityMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_TaxPeriodAxis=ema_TwoZeroZeroSixToTwoZeroOneZeroMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=ema_NovaScotiaPowerIncMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_IncomeTaxAuthorityNameAxis=us-gaap_CanadaRevenueAgencyMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |