Segment Information (Narrative) (Details)	12 Months Ended
Dec. 31, 2020 Segments
5. Segment Information
Segment Reporting, Factors Used to Identify Entity's Reportable Segments	Emera manages its reportable segments separately due in part to their different operating, regulatory and geographical environments. Segments are reported based on each subsidiary’s contribution of revenues, net income attributable to common shareholders and total assets, as reported to the Company’s chief operating decision maker.
Number of reportable segments	5

Description of the factors used to identify reportable segments, including the basis of organization (for example, whether management has chosen to organize the enterprise around differences in products and services, geographic areas, regulatory environments, or a combination of factors and whether operating segments have been aggregated to reportable segments).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 21
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8721-108599

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