Description of Business - Regulated Utilities (Details)	Jun. 30, 2020
Wataynikaneyap Power Limited Partnership
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%
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%

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

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=114001798&loc=d3e33918-111571

+ Details

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- Definition

The equity interest of noncontrolling shareholders, partners or other equity holders in consolidated entity.

+ References

No definition available.

+ Details

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- Definition

The parent entity's interest in net assets of the subsidiary, expressed as a percentage.

+ References

No definition available.

+ Details

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- 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

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- Details

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- Details

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- Details

Name:	srt_OwnershipAxis=fts_ITCHoldingsCorp.Member
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- Details

Name:	srt_OwnershipAxis=fts_CaribbeanUtilitiesCompanyLtd.Member
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