XML 50 R81.htm IDEA: XBRL DOCUMENT v3.20.1

Revenue (Disaggregation) (Details) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	$ 6,111	$ 6,524
Total operating revenues	6,111	6,524
Florida Electric Utility
Disaggregation of Revenue [Line Items]
Total operating revenues	2,607	2,679
Canadian Electric Utilities
Disaggregation of Revenue [Line Items]
Total operating revenues	1,430	1,440
Other Electric Utilities
Disaggregation of Revenue [Line Items]
Total operating revenues	744	745
Gas Utilities and Infrastructure
Disaggregation of Revenue [Line Items]
Total operating revenues	1,119	1,098
Other
Disaggregation of Revenue [Line Items]
Total operating revenues	282	661
Operating
Disaggregation of Revenue [Line Items]
Total operating revenues	6,111	6,524
Operating | Florida Electric Utility
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	2,607	2,679
Total operating revenues	2,596	2,670
Operating | Canadian Electric Utilities
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	1,430	1,440
Total operating revenues	1,429	1,437
Operating | Other Electric Utilities
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	744	745
Total operating revenues	744	745
Operating | Gas Utilities and Infrastructure
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	1,119	1,098
Total operating revenues	1,097	1,062
Operating | Other
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	282	661
Total operating revenues	245	610
Eliminations
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	(71)	(99)
Total operating revenues	(43)	(54)
Eliminations | Florida Electric Utility
Disaggregation of Revenue [Line Items]
Total operating revenues	11	9
Eliminations | Canadian Electric Utilities
Disaggregation of Revenue [Line Items]
Total operating revenues	1	3
Eliminations | Other Electric Utilities
Disaggregation of Revenue [Line Items]
Total operating revenues	0	0
Eliminations | Gas Utilities and Infrastructure
Disaggregation of Revenue [Line Items]
Total operating revenues	22	36
Eliminations | Other
Disaggregation of Revenue [Line Items]
Total operating revenues	37	51
Non-Regulated
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	261	628
Total operating revenues	261	628
Non-Regulated | Capacity
Disaggregation of Revenue [Line Items]
Total operating revenues	38	136
Non-Regulated | Operating | Florida Electric Utility
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Non-Regulated | Operating | Florida Electric Utility | Capacity
Disaggregation of Revenue [Line Items]
Total operating revenues	0	0
Non-Regulated | Operating | Canadian Electric Utilities
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Non-Regulated | Operating | Canadian Electric Utilities | Capacity
Disaggregation of Revenue [Line Items]
Total operating revenues	0	0
Non-Regulated | Operating | Other Electric Utilities
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Non-Regulated | Operating | Other Electric Utilities | Capacity
Disaggregation of Revenue [Line Items]
Total operating revenues	0	0
Non-Regulated | Operating | Gas Utilities and Infrastructure
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	16	18
Non-Regulated | Operating | Gas Utilities and Infrastructure | Capacity
Disaggregation of Revenue [Line Items]
Total operating revenues	0	0
Non-Regulated | Operating | Other
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	282	661
Non-Regulated | Operating | Other | Capacity
Disaggregation of Revenue [Line Items]
Total operating revenues	38	136
Non-Regulated | Eliminations
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	(37)	(51)
Non-Regulated | Eliminations | Capacity
Disaggregation of Revenue [Line Items]
Total operating revenues	0	0
Electric | Regulated
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	4,769	4,852
Total operating revenues	4,769	4,852
Electric | Regulated | Operating | Florida Electric Utility
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	2,607	2,679
Electric | Regulated | Operating | Canadian Electric Utilities
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	1,430	1,440
Electric | Regulated | Operating | Other Electric Utilities
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	744	745
Electric | Regulated | Operating | Gas Utilities and Infrastructure
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Electric | Regulated | Operating | Other
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Electric | Regulated | Eliminations
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	(12)	(12)
Electric | Regulated | Residential
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	2,409	2,376
Electric | Regulated | Residential | Operating | Florida Electric Utility
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	1,387	1,384
Electric | Regulated | Residential | Operating | Canadian Electric Utilities
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	746	731
Electric | Regulated | Residential | Operating | Other Electric Utilities
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	276	261
Electric | Regulated | Residential | Operating | Gas Utilities and Infrastructure
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Electric | Regulated | Residential | Operating | Other
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Electric | Regulated | Residential | Eliminations
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Electric | Regulated | Commercial
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	1,484	1,510
Electric | Regulated | Commercial | Operating | Florida Electric Utility
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	745	755
Electric | Regulated | Commercial | Operating | Canadian Electric Utilities
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	400	405
Electric | Regulated | Commercial | Operating | Other Electric Utilities
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	339	350
Electric | Regulated | Commercial | Operating | Gas Utilities and Infrastructure
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Electric | Regulated | Commercial | Operating | Other
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Electric | Regulated | Commercial | Eliminations
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Electric | Regulated | Industrial
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	461	488
Electric | Regulated | Industrial | Operating | Florida Electric Utility
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	207	209
Electric | Regulated | Industrial | Operating | Canadian Electric Utilities
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	210	233
Electric | Regulated | Industrial | Operating | Other Electric Utilities
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	44	46
Electric | Regulated | Industrial | Operating | Gas Utilities and Infrastructure
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Electric | Regulated | Industrial | Operating | Other
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Electric | Regulated | Industrial | Eliminations
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Electric | Regulated | Other Electric And Regulatory
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	304	371
Electric | Regulated | Other Electric And Regulatory | Operating | Florida Electric Utility
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	246	312
Electric | Regulated | Other Electric And Regulatory | Operating | Canadian Electric Utilities
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	45	43
Electric | Regulated | Other Electric And Regulatory | Operating | Other Electric Utilities
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	13	16
Electric | Regulated | Other Electric And Regulatory | Operating | Gas Utilities and Infrastructure
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Electric | Regulated | Other Electric And Regulatory | Operating | Other
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Electric | Regulated | Other Electric And Regulatory | Eliminations
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Electric | Regulated | Other
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	111	107
Electric | Regulated | Other | Operating | Florida Electric Utility
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	22	19
Electric | Regulated | Other | Operating | Canadian Electric Utilities
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	29	28
Electric | Regulated | Other | Operating | Other Electric Utilities
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	72	72
Electric | Regulated | Other | Operating | Gas Utilities and Infrastructure
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Electric | Regulated | Other | Operating | Other
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Electric | Regulated | Other | Eliminations
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	(12)	(12)
Gas | Regulated
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	1,081	1,044
Total operating revenues	1,081	1,044
Gas | Regulated | Operating | Florida Electric Utility
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Gas | Regulated | Operating | Canadian Electric Utilities
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Gas | Regulated | Operating | Other Electric Utilities
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Gas | Regulated | Operating | Gas Utilities and Infrastructure
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	1,103	1,080
Gas | Regulated | Operating | Other
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Gas | Regulated | Eliminations
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	(22)	(36)
Gas | Regulated | Residential
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	502	492
Gas | Regulated | Residential | Operating | Florida Electric Utility
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Gas | Regulated | Residential | Operating | Canadian Electric Utilities
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Gas | Regulated | Residential | Operating | Other Electric Utilities
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Gas | Regulated | Residential | Operating | Gas Utilities and Infrastructure
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	502	492
Gas | Regulated | Residential | Operating | Other
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Gas | Regulated | Residential | Eliminations
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Gas | Regulated | Commercial
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	298	291
Gas | Regulated | Commercial | Operating | Florida Electric Utility
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Gas | Regulated | Commercial | Operating | Canadian Electric Utilities
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Gas | Regulated | Commercial | Operating | Other Electric Utilities
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Gas | Regulated | Commercial | Operating | Gas Utilities and Infrastructure
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	298	291
Gas | Regulated | Commercial | Operating | Other
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Gas | Regulated | Commercial | Eliminations
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Gas | Regulated | Industrial
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	50	49
Gas | Regulated | Industrial | Operating | Florida Electric Utility
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Gas | Regulated | Industrial | Operating | Canadian Electric Utilities
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Gas | Regulated | Industrial | Operating | Other Electric Utilities
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Gas | Regulated | Industrial | Operating | Gas Utilities and Infrastructure
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	50	49
Gas | Regulated | Industrial | Operating | Other
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Gas | Regulated | Industrial | Eliminations
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Gas | Regulated | Finance Income
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	60	57
Gas | Regulated | Finance Income | Operating | Florida Electric Utility
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Gas | Regulated | Finance Income | Operating | Canadian Electric Utilities
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Gas | Regulated | Finance Income | Operating | Other Electric Utilities
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Gas | Regulated | Finance Income | Operating | Gas Utilities and Infrastructure
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	60	57
Gas | Regulated | Finance Income | Operating | Other
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Gas | Regulated | Finance Income | Eliminations
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Gas | Regulated | Other
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	171	155
Gas | Regulated | Other | Operating | Florida Electric Utility
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Gas | Regulated | Other | Operating | Canadian Electric Utilities
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Gas | Regulated | Other | Operating | Other Electric Utilities
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Gas | Regulated | Other | Operating | Gas Utilities and Infrastructure
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	193	191
Gas | Regulated | Other | Operating | Other
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Gas | Regulated | Other | Eliminations
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	(22)	(36)
Marketing and trading margin | Non-Regulated
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	31	115
Marketing and trading margin | Non-Regulated | Operating | Florida Electric Utility
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Marketing and trading margin | Non-Regulated | Operating | Canadian Electric Utilities
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Marketing and trading margin | Non-Regulated | Operating | Other Electric Utilities
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Marketing and trading margin | Non-Regulated | Operating | Gas Utilities and Infrastructure
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Marketing and trading margin | Non-Regulated | Operating | Other
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	31	115
Marketing and trading margin | Non-Regulated | Eliminations
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Energy sales | Non-Regulated
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	68	293
Energy sales | Non-Regulated | Operating | Florida Electric Utility
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Energy sales | Non-Regulated | Operating | Canadian Electric Utilities
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Energy sales | Non-Regulated | Operating | Other Electric Utilities
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Energy sales | Non-Regulated | Operating | Gas Utilities and Infrastructure
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Energy sales | Non-Regulated | Operating | Other
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	80	309
Energy sales | Non-Regulated | Eliminations
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	(12)	(16)
Other | Non-Regulated
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	22	30
Other | Non-Regulated | Operating | Florida Electric Utility
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Other | Non-Regulated | Operating | Canadian Electric Utilities
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Other | Non-Regulated | Operating | Other Electric Utilities
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Other | Non-Regulated | Operating | Gas Utilities and Infrastructure
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	16	18
Other | Non-Regulated | Operating | Other
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	31	47
Other | Non-Regulated | Eliminations
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	(25)	(35)
Mark-To-Market | Non-Regulated
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	102	54
Mark-To-Market | Non-Regulated | Operating | Florida Electric Utility
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Mark-To-Market | Non-Regulated | Operating | Canadian Electric Utilities
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Mark-To-Market | Non-Regulated | Operating | Other Electric Utilities
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Mark-To-Market | Non-Regulated | Operating | Gas Utilities and Infrastructure
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	0	0
Mark-To-Market | Non-Regulated | Operating | Other
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	102	54
Mark-To-Market | Non-Regulated | Eliminations
Disaggregation of Revenue [Line Items]
Revenue from contract with customer	$ 0	$ 0

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

X

- Definition

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130543-203045

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130545-203045

+ Details

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

X

- Definition

Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=115929826&loc=d3e8736-108599

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=115929826&loc=d3e8933-108599

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=115929826&loc=d3e8736-108599

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(1))
-URI http://asc.fasb.org/extlink&oid=116634182&loc=SL114868664-224227

+ Details

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

X

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=ema_FloridaElectricUtilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=ema_CanadianElectricUtilitiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=ema_OtherElectricUtilitiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=ema_GasUtilitiesAndInfrastructureMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=us-gaap_CorporateAndOtherMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_ConsolidationItemsAxis=us-gaap_OperatingSegmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_ConsolidationItemsAxis=srt_ConsolidationEliminationsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_PublicUtilityRegulatedOrUnregulatedStatusAxis=us-gaap_UnregulatedOperationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_RecordedUnconditionalPurchaseObligationByCategoryOfItemPurchasedAxis=us-gaap_CapacityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_ProductOrServiceAxis=us-gaap_ElectricityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_PublicUtilityRegulatedOrUnregulatedStatusAxis=us-gaap_RegulatedOperationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_MajorCustomersAxis=ema_ResidentialCustomerClassMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_MajorCustomersAxis=ema_CommercialCustomerClassMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_MajorCustomersAxis=ema_IndustrialCustomerClassMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_MajorCustomersAxis=ema_OtherElectricAndRegulatoryMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_MajorCustomersAxis=us-gaap_OtherCustomerMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_ProductOrServiceAxis=us-gaap_OilAndGasMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_MajorCustomersAxis=ema_FinanceIncomeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_ProductOrServiceAxis=us-gaap_EnergyCommoditiesAndServiceMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_ProductOrServiceAxis=us-gaap_EnergyServiceMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_ProductOrServiceAxis=ema_OtherProjectAndServicesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_ProductOrServiceAxis=ema_MarkToMarketMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: