Description of Business - Regulated Utilities (Details)	Dec. 31, 2024 station community company MW
Wataynikaneyap Power
Public Utilities, General Disclosures [Line Items]
Equity investment ownership (percent)	39.00%
Belize Electricity
Public Utilities, General Disclosures [Line Items]
Equity investment ownership (percent)	33.00%
TEP and UNS Electric
Public Utilities, General Disclosures [Line Items]
Generating capacity (MW)	3,442
TEP and UNS Electric \| Solar
Public Utilities, General Disclosures [Line Items]
Generating capacity (MW)	68
TEP and UNS Electric \| Wind
Public Utilities, General Disclosures [Line Items]
Generating capacity (MW)	250
Central Hudson \| Gas-Fired and Hydroelectric Power Generation
Public Utilities, General Disclosures [Line Items]
Generating capacity (MW)	43
FortisBC Electric \| Hydroelectric Power Generation
Public Utilities, General Disclosures [Line Items]
Generating capacity (MW)	225
Generating facilities \| station	4
Generating facilities, operating, maintenance and management services \| station	5
Newfoundland Power
Public Utilities, General Disclosures [Line Items]
Generating capacity (MW)	145
Newfoundland Power \| Hydroelectric Power Generation
Public Utilities, General Disclosures [Line Items]
Generating capacity (MW)	98
Maritime Electric
Public Utilities, General Disclosures [Line Items]
Generating capacity (MW)	90
FortisOntario
Public Utilities, General Disclosures [Line Items]
Generating capacity (MW)	3
Number of utilities \| company	3
Fortis \| Wataynikaneyap Power
Public Utilities, General Disclosures [Line Items]
Partnership with First Nation communities, number \| community	24
Number of remote First Nation communities \| community	17
Caribbean Utilities \| Diesel
Public Utilities, General Disclosures [Line Items]
Generating capacity (MW)	166
Fortis Turks and Caicos
Public Utilities, General Disclosures [Line Items]
Generating capacity (MW)	99
Number of utilities \| company	2
Fortis Turks and Caicos \| Solar
Public Utilities, General Disclosures [Line Items]
Generating capacity (MW)	4
Fortis Turks and Caicos \| Diesel
Public Utilities, General Disclosures [Line Items]
Generating capacity (MW)	95
ITC
Public Utilities, General Disclosures [Line Items]
Controlling ownership interest (percent)	80.10%
Noncontrolling ownership (percent)	19.90%
Caribbean Utilities
Public Utilities, General Disclosures [Line Items]
Controlling ownership interest (percent)	60.00%

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The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 323
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481687/323-10-50-3

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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.

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