XML 130 R115.htm IDEA: XBRL DOCUMENT v3.6.0.2

Fair Values (fair value of the Level 3 financial Liabilities) (Details) - Designated as Hedging Instrument [Member] CAD in Millions	12 Months Ended
	Dec. 31, 2016 CAD
Derivative Financial Instruments, Liabilities [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	CAD 277
Total realized and unrealized gains (losses) included in non-regulated operating revenues	112
Net transfers out of Level 3	0
Ending Balance	389
Regulated fuel for generation and purchased power [Member] | Derivative Financial Instruments, Liabilities [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Increase (reduction) in benefit included in regulated and nonregulated fuel for generation and purchased power	0
Non-regulated fuel for generation and purchased power [Member] | Derivative Financial Instruments, Liabilities [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Increase (reduction) in benefit included in regulated and nonregulated fuel for generation and purchased power	0
Regulatory Liabilities [Member] | Derivative Financial Instruments, Liabilities [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Unrealized gains (losses) included in regulatory assets or liabilities	0
Regulatory Deferral Hedge [Member] | Physical natural gas purchases and sales [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	0
Total realized and unrealized gains (losses) included in non-regulated operating revenues	0
Net transfers out of Level 3	0
Ending Balance	0
Regulatory Deferral Hedge [Member] | Physical natural gas purchases and sales [Member] | Regulated fuel for generation and purchased power [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Increase (reduction) in benefit included in regulated and nonregulated fuel for generation and purchased power	0
Regulatory Deferral Hedge [Member] | Physical natural gas purchases and sales [Member] | Non-regulated fuel for generation and purchased power [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Increase (reduction) in benefit included in regulated and nonregulated fuel for generation and purchased power	0
Regulatory Deferral Hedge [Member] | Physical natural gas purchases and sales [Member] | Regulatory Liabilities [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Unrealized gains (losses) included in regulatory assets or liabilities	0
Cash Flow Hedging And Held for Trading Hedge [Member] | Natural Gas [Member] | Derivative Financial Instruments, Liabilities [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	279
Total realized and unrealized gains (losses) included in non-regulated operating revenues	110
Net transfers out of Level 3	0
Ending Balance	389
Cash Flow Hedging And Held for Trading Hedge [Member] | Natural Gas [Member] | Regulated fuel for generation and purchased power [Member] | Derivative Financial Instruments, Liabilities [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Increase (reduction) in benefit included in regulated and nonregulated fuel for generation and purchased power	0
Cash Flow Hedging And Held for Trading Hedge [Member] | Natural Gas [Member] | Non-regulated fuel for generation and purchased power [Member] | Derivative Financial Instruments, Liabilities [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Increase (reduction) in benefit included in regulated and nonregulated fuel for generation and purchased power	0
Cash Flow Hedging And Held for Trading Hedge [Member] | Natural Gas [Member] | Regulatory Liabilities [Member] | Derivative Financial Instruments, Liabilities [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Unrealized gains (losses) included in regulatory assets or liabilities	0
Cash Flow Hedging And Held for Trading Hedge [Member] | Power [Member] | Derivative Financial Instruments, Liabilities [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	(2)
Total realized and unrealized gains (losses) included in non-regulated operating revenues	2
Net transfers out of Level 3	0
Ending Balance	0
Cash Flow Hedging And Held for Trading Hedge [Member] | Power [Member] | Regulated fuel for generation and purchased power [Member] | Derivative Financial Instruments, Liabilities [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Increase (reduction) in benefit included in regulated and nonregulated fuel for generation and purchased power	0
Cash Flow Hedging And Held for Trading Hedge [Member] | Power [Member] | Non-regulated fuel for generation and purchased power [Member] | Derivative Financial Instruments, Liabilities [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Increase (reduction) in benefit included in regulated and nonregulated fuel for generation and purchased power	0
Cash Flow Hedging And Held for Trading Hedge [Member] | Power [Member] | Regulatory Liabilities [Member] | Derivative Financial Instruments, Liabilities [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Unrealized gains (losses) included in regulatory assets or liabilities	CAD 0

X

- Definition

Total amount of unrealized (holding) gain (loss) and realized gain (loss) which is included in the statement of income (or changes in net liabilities) related to those liabilities still held at the reporting date for which fair value is measured on a recurring basis using significant unobservable inputs (Level 3).

+ References

No definition available.

+ Details

Name:	ema_FairValueLiabilitiesMeasuredOnRecurringBasisTotalUnrealizedAndRealizedGainLoss
Namespace Prefix:	ema_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

X

- Definition

Amount of unrealized (holding) gain (loss) which is included in the statement of income (or changes in net assets) related to those liabilities still held at the reporting date for which fair value is measured on a recurring basis using significant unobservable inputs (Level 3).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

+ Details

Name:	us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisChangeInUnrealizedGainLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

X

- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

+ Details

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

X

- Definition

Amount of gain (loss) recognized on the income statement for financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

+ Details

Name:	us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

X

- Definition

Amount of transfers of financial instrument classified as a liability into (out of) level 3 of the fair value hierarchy.

+ References

No definition available.

+ Details

Name:	us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityTransfersNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

X

- Definition

Fair value of financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

+ Details

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

X

- Details

Name:	us-gaap_HedgingDesignationAxis=us-gaap_DesignatedAsHedgingInstrumentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FairValueByLiabilityClassAxis=us-gaap_DerivativeFinancialInstrumentsLiabilitiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_IncomeStatementLocationAxis=ema_RegulatedFuelForGenerationAndPurchasedPowerMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_IncomeStatementLocationAxis=ema_NonRegulatedFuelForGenerationAndPurchasedPowerMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_IncomeStatementLocationAxis=ema_RegulatoryLiabilitiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis=ema_RegulatoryDeferralHedgeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=ema_PhysicalNaturalGasPurchasesAndSalesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis=ema_CashFlowHedgingAndHeldForTradingHedgeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_EnergyAxis=ema_NaturalGasMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_EnergyAxis=ema_PowerMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: