XML 119 R104.htm IDEA: XBRL DOCUMENT v3.6.0.2

Derivatives (Changes in Realized and Unrealized Gains (Losses) with Respect to Derivatives Receiving Regulatory Deferral) (Details) - CAD CAD in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized Gain (Loss) on Derivatives	CAD (258.0)	CAD (96.0)
Designated as Hedging Instrument [Member] | Regulatory Deferral Hedge [Member] | Commodity swaps and forwards [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	163.0	(30.0)
Designated as Hedging Instrument [Member] | Regulatory Deferral Hedge [Member] | Commodity swaps and forwards [Member] | Regulatory Assets [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized Gain (Loss) on Derivatives	40.0	(24.0)
Derivative, Gain (Loss) on Derivative, Net	0.0	(3.0)
Designated as Hedging Instrument [Member] | Regulatory Deferral Hedge [Member] | Commodity swaps and forwards [Member] | Regulatory Liabilities [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized Gain (Loss) on Derivatives	101.0	1.0
Derivative, Gain (Loss) on Derivative, Net	0.0	0.0
Designated as Hedging Instrument [Member] | Regulatory Deferral Hedge [Member] | Commodity swaps and forwards [Member] | Property, Plant and Equipment [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	0.0	0.0
Designated as Hedging Instrument [Member] | Regulatory Deferral Hedge [Member] | Commodity swaps and forwards [Member] | Inventory [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	5.0	12.0
Designated as Hedging Instrument [Member] | Regulatory Deferral Hedge [Member] | Commodity swaps and forwards [Member] | Non-regulated fuel for generation and purchased power [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	17.0	(16.0)
Designated as Hedging Instrument [Member] | Regulatory Deferral Hedge [Member] | Physical natural gas purchases and sales [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	(2.0)	2.0
Designated as Hedging Instrument [Member] | Regulatory Deferral Hedge [Member] | Physical natural gas purchases and sales [Member] | Regulatory Assets [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized Gain (Loss) on Derivatives	0.0	0.0
Derivative, Gain (Loss) on Derivative, Net	0.0	0.0
Designated as Hedging Instrument [Member] | Regulatory Deferral Hedge [Member] | Physical natural gas purchases and sales [Member] | Regulatory Liabilities [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized Gain (Loss) on Derivatives	(1.0)	9.0
Derivative, Gain (Loss) on Derivative, Net	0.0	0.0
Designated as Hedging Instrument [Member] | Regulatory Deferral Hedge [Member] | Physical natural gas purchases and sales [Member] | Property, Plant and Equipment [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	0.0	0.0
Designated as Hedging Instrument [Member] | Regulatory Deferral Hedge [Member] | Physical natural gas purchases and sales [Member] | Inventory [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	0.0	0.0
Designated as Hedging Instrument [Member] | Regulatory Deferral Hedge [Member] | Physical natural gas purchases and sales [Member] | Non-regulated fuel for generation and purchased power [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	(1.0)	(7.0)
Designated as Hedging Instrument [Member] | Regulatory Deferral Hedge [Member] | Foreign Exchange Forward [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	(90.0)	103.0
Designated as Hedging Instrument [Member] | Regulatory Deferral Hedge [Member] | Foreign Exchange Forward [Member] | Regulatory Assets [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized Gain (Loss) on Derivatives	(2.0)	(7.0)
Derivative, Gain (Loss) on Derivative, Net	12.0	0.0
Designated as Hedging Instrument [Member] | Regulatory Deferral Hedge [Member] | Foreign Exchange Forward [Member] | Regulatory Liabilities [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized Gain (Loss) on Derivatives	(30.0)	173.0
Derivative, Gain (Loss) on Derivative, Net	(8.0)	0.0
Designated as Hedging Instrument [Member] | Regulatory Deferral Hedge [Member] | Foreign Exchange Forward [Member] | Property, Plant and Equipment [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	0.0	(1.0)
Designated as Hedging Instrument [Member] | Regulatory Deferral Hedge [Member] | Foreign Exchange Forward [Member] | Inventory [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	(44.0)	(44.0)
Designated as Hedging Instrument [Member] | Regulatory Deferral Hedge [Member] | Foreign Exchange Forward [Member] | Non-regulated fuel for generation and purchased power [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Gain (Loss) on Derivative, Net	CAD (18.0)	CAD (18.0)

X

- Definition

Amount of increase (decrease) in the fair value of derivatives recognized in the income statement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=64837297&loc=SL5618551-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (a),(c),(d),(e)
-URI http://asc.fasb.org/extlink&oid=64837297&loc=SL5624171-113959

+ Details

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

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

X

- Definition

The net change in the difference between the fair value and the carrying value, or in the comparative fair values, of derivative instruments, including options, swaps, futures, and forward contracts, held at each balance sheet date, that was included in earnings for the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3602-108585

+ Details

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

X

- Details

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

X

- Details

Name:	us-gaap_IncomeStatementLocationAxis=ema_RegulatoryAssetsMember
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_IncomeStatementLocationAxis=us-gaap_PropertyPlantAndEquipmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_IncomeStatementLocationAxis=ema_InventoryMember
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_DerivativeInstrumentRiskAxis=ema_PhysicalNaturalGasPurchasesAndSalesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

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