XML 108 R91.htm IDEA: XBRL DOCUMENT v3.7.0.1

Income Taxes (Carry Overs) (Details) - CAD CAD in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Tax Loss Carry Forwards [Abstract]
Deferred Tax Assets, Tax Credit Carryforwards	CAD 318	CAD 7
Tax Loss Carry Forwards Valuation Allowance [Abstract]
Deferred Tax Assets, Valuation Allowance	58	18
Loss carry forwards and investments [Member]
Tax Loss Carry Forwards Valuation Allowance [Abstract]
Deferred Tax Assets, Valuation Allowance	58	18
Domestic Tax Authority [Member]
Tax Loss Carry Forwards [Abstract]
Deferred Tax Assets, Operating Loss Carryforwards	199	103
Deferred Tax Assets, Tax Credit Carryforwards	0	0
Domestic Tax Authority [Member] | Capital Loss Carryforward [Member]
Tax Loss Carry Forwards [Abstract]
Deferred Tax Assets, Operating Loss Carryforwards	77	84
Deferred Tax Assets Uncertain Realization [Abstract]
Deferred Tax Assets Uncertain Realization	16
Valuation Allowance	(16)
Net Deferred Tax Assets	0
Domestic Tax Authority [Member] | Operating Loss Carryforward [Member]
Deferred Tax Assets Uncertain Realization [Abstract]
Deferred Tax Assets Uncertain Realization	61
Valuation Allowance	(27)
Net Deferred Tax Assets	CAD 34
Domestic Tax Authority [Member] | Operating Loss Carryforward [Member] | Maximum [Member]
Deferred Tax Assets Uncertain Realization [Abstract]
Deferred Tax Asset Expiration Period	2036
Domestic Tax Authority [Member] | Operating Loss Carryforward [Member] | Minimum [Member]
Deferred Tax Assets Uncertain Realization [Abstract]
Deferred Tax Asset Expiration Period	2026
Foreign Tax Authority [Member]
Tax Loss Carry Forwards [Abstract]
Deferred Tax Assets, Operating Loss Carryforwards	CAD 2,595	48
Deferred Tax Assets, Tax Credit Carryforwards	318	30
Foreign Tax Authority [Member] | Capital Loss Carryforward [Member]
Tax Loss Carry Forwards [Abstract]
Deferred Tax Assets, Operating Loss Carryforwards	14	4
Deferred Tax Assets Uncertain Realization [Abstract]
Deferred Tax Assets Uncertain Realization	3
Valuation Allowance	(3)
Net Deferred Tax Assets	CAD 0
Foreign Tax Authority [Member] | Capital Loss Carryforward [Member] | Maximum [Member]
Deferred Tax Assets Uncertain Realization [Abstract]
Deferred Tax Asset Expiration Period	2019
Foreign Tax Authority [Member] | Capital Loss Carryforward [Member] | Minimum [Member]
Deferred Tax Assets Uncertain Realization [Abstract]
Deferred Tax Asset Expiration Period	2018
Foreign Tax Authority [Member] | Operating Loss Carryforward [Member]
Deferred Tax Assets Uncertain Realization [Abstract]
Deferred Tax Assets Uncertain Realization	CAD 908
Valuation Allowance	0
Net Deferred Tax Assets	CAD 908
Foreign Tax Authority [Member] | Operating Loss Carryforward [Member] | Maximum [Member]
Deferred Tax Assets Uncertain Realization [Abstract]
Deferred Tax Asset Expiration Period	2036
Foreign Tax Authority [Member] | Operating Loss Carryforward [Member] | Minimum [Member]
Deferred Tax Assets Uncertain Realization [Abstract]
Deferred Tax Asset Expiration Period	2024
Foreign Tax Authority [Member] | State Operating Loss Carryforward [Member]
Tax Loss Carry Forwards [Abstract]
Deferred Tax Assets, Operating Loss Carryforwards	CAD 1,183	225
Deferred Tax Assets Uncertain Realization [Abstract]
Deferred Tax Assets Uncertain Realization	45
Valuation Allowance	(1)
Net Deferred Tax Assets	CAD 44
Foreign Tax Authority [Member] | State Operating Loss Carryforward [Member] | Maximum [Member]
Deferred Tax Assets Uncertain Realization [Abstract]
Deferred Tax Asset Expiration Period	2036
Foreign Tax Authority [Member] | State Operating Loss Carryforward [Member] | Minimum [Member]
Deferred Tax Assets Uncertain Realization [Abstract]
Deferred Tax Asset Expiration Period	2017
Foreign Tax Authority [Member] | Tax credit carry forwards [Member]
Deferred Tax Assets Uncertain Realization [Abstract]
Deferred Tax Assets Uncertain Realization	CAD 318
Valuation Allowance	0
Net Deferred Tax Assets	CAD 318
Foreign Tax Authority [Member] | Tax credit carry forwards [Member] | Maximum [Member]
Deferred Tax Assets Uncertain Realization [Abstract]
Deferred Tax Asset Expiration Period	2036
Foreign Tax Authority [Member] | Tax credit carry forwards [Member] | Minimum [Member]
Deferred Tax Assets Uncertain Realization [Abstract]
Deferred Tax Asset Expiration Period	2019
Other Tax Authority [Member]
Tax Loss Carry Forwards [Abstract]
Deferred Tax Assets, Operating Loss Carryforwards	CAD 22	CAD 14
Other Tax Authority [Member] | Operating Loss Carryforward [Member]
Deferred Tax Assets Uncertain Realization [Abstract]
Deferred Tax Assets Uncertain Realization	3
Valuation Allowance	(3)
Net Deferred Tax Assets	CAD 0
Other Tax Authority [Member] | Operating Loss Carryforward [Member] | Maximum [Member]
Deferred Tax Assets Uncertain Realization [Abstract]
Deferred Tax Asset Expiration Period	2023
Other Tax Authority [Member] | Operating Loss Carryforward [Member] | Minimum [Member]
Deferred Tax Assets Uncertain Realization [Abstract]
Deferred Tax Asset Expiration Period	2017

X

- Definition

Deferred Tax Asset Expiration Period.

+ References

No definition available.

+ Details

Name:	ema_DeferredTaxAssetExpirationPeriod
Namespace Prefix:	ema_
Data Type:	xbrli:gYearItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Deferred tax assets for which realization is unceratin.

+ References

No definition available.

+ Details

Name:	ema_DeferredTaxAssetsUncertainRealization
Namespace Prefix:	ema_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- References

No definition available.

+ Details

Name:	ema_DeferredTaxAssetsUncertainRealizationAbstract
Namespace Prefix:	ema_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Deferred Tax Valuation Allowance Uncertain Realization

+ References

No definition available.

+ Details

Name:	ema_DeferredTaxValuationAllowanceUncertainRealization
Namespace Prefix:	ema_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- Definition

Net Deferred Tax Assets Uncertain Realization

+ References

No definition available.

+ Details

Name:	ema_NetDeferredTaxAssetsUncertainRealization
Namespace Prefix:	ema_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- References

No definition available.

+ Details

Name:	ema_TaxLossCarryForwardsAbstract
Namespace Prefix:	ema_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- References

No definition available.

+ Details

Name:	ema_TaxLossCarryForwardsValuationAllowanceAbstract
Namespace Prefix:	ema_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Amount before allocation of valuation allowances of deferred tax asset attributable to deductible operating loss carryforwards.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 25
-Paragraph 20
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=68052875&loc=d3e28680-109314

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=65882285&loc=d3e32621-109319

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=65882285&loc=d3e32632-109319

+ Details

Name:	us-gaap_DeferredTaxAssetsOperatingLossCarryforwards
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Amount, before allocation of a valuation allowances, of deferred tax assets attributable to deductible tax credit carryforwards including, but not limited to, research, foreign, general business, alternative minimum tax, and other deductible tax credit carryforwards.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=65882285&loc=d3e32621-109319

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=65882285&loc=d3e32559-109319

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Carryforwards
-URI http://asc.fasb.org/extlink&oid=6506874

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=65882285&loc=d3e32632-109319

+ Details

Name:	us-gaap_DeferredTaxAssetsTaxCreditCarryforwards
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=65882285&loc=d3e32537-109319

+ Details

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

X

- Details

Name:	us-gaap_TaxCreditCarryforwardAxis=ema_LossCarryForwardsAndInvestmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_IncomeTaxAuthorityAxis=us-gaap_DomesticCountryMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_TaxCreditCarryforwardAxis=us-gaap_CapitalLossCarryforwardMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_TaxCreditCarryforwardAxis=ema_OperatingLossCarryforwardMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_IncomeTaxAuthorityAxis=us-gaap_ForeignCountryMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_TaxCreditCarryforwardAxis=ema_UnitedStatesStateTaxAuthorityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_TaxCreditCarryforwardAxis=ema_TaxCreditCarryForwardsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_IncomeTaxAuthorityAxis=ema_OtherTaxAuthorityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: