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Amount of contractual obligation to be paid after fifth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

No definition available.

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Amount of contractual obligation to be paid in fifth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

No definition available.

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Amount of contractual obligation to be paid in fourth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

No definition available.

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Amount of contractual obligation to be paid in next fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

No definition available.

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Amount of contractual obligation to be paid in second fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

No definition available.

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Amount of contractual obligation to be paid in third fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

No definition available.

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Period covered by the long-term purchase commitment, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

No definition available.

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Reflects the estimated amount of loss from the specified contingency as of the balance sheet date.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 4
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-URI http://asc.fasb.org/extlink&oid=121557415&loc=d3e14435-108349

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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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If estimable, describe the recovery that could be expected to result from a right to proceed against a third party such as an insurer or co-defendant.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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The difference between the maximum amount of estimated loss and the amount recorded as of the balance sheet date.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
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Amount of receivable related to a loss contingency accrual. For example, an insurance recovery receivable.

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Data Type:	xbrli:monetaryItemType
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- References

No definition available.

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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.

No definition available.

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Data Type:	xbrli:stringItemType
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Period Type:	duration

Amount of transaction price allocated to performance obligation that has not been recognized as revenue.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 13
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-URI http://asc.fasb.org/extlink&oid=121604090&loc=SL49130556-203045

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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Name:	srt_CounterpartyNameAxis=ema_PeoplesGasSystemDivisionMember
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Data Type:	na
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Name:	us-gaap_PublicUtilityAxis=ema_MaritimeLinkProjectMember
Namespace Prefix:
Data Type:	na
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Name:	srt_CounterpartyNameAxis=ema_NspMaritimeLinkIncMember
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Data Type:	na
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Name:	srt_StatementScenarioAxis=us-gaap_ScenarioPlanMember
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Data Type:	na
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Name:	srt_ConsolidatedEntitiesAxis=ema_NovaScotiaPowerIncMember
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Name:	us-gaap_RecordedUnconditionalPurchaseObligationByCategoryOfItemPurchasedAxis=us-gaap_ElectricityPurchasedMember
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Data Type:	na
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Name:	us-gaap_RecordedUnconditionalPurchaseObligationByCategoryOfItemPurchasedAxis=us-gaap_OilAndGasServiceMember
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Data Type:	na
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Data Type:	na
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Name:	us-gaap_RecordedUnconditionalPurchaseObligationByCategoryOfItemPurchasedAxis=ema_FuelAndGasSupplyMember
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Data Type:	na
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Name:	us-gaap_RecordedUnconditionalPurchaseObligationByCategoryOfItemPurchasedAxis=us-gaap_ServiceAgreementsMember
Namespace Prefix:
Data Type:	na
Balance Type:
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Name:	us-gaap_RecordedUnconditionalPurchaseObligationByCategoryOfItemPurchasedAxis=us-gaap_EquityMethodInvestmentsMember
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Data Type:	na
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Name:	us-gaap_RecordedUnconditionalPurchaseObligationByCategoryOfItemPurchasedAxis=us-gaap_LeaseAgreementsMember
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