Earnings Per Share, Effect Of Five-Percentage-Point Change On Exchange Rate

No definition available.

Name:	fts_EarningsPerShareEffectOfFivePercentagePointChangeOnExchangeRate
Namespace Prefix:	fts_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

Net Investment In Foreign Operation, Amount Not Hedged

+ References

No definition available.

+ Details

Name:	fts_NetInvestmentInForeignOperationAmountNotHedged
Namespace Prefix:	fts_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of the hedged item as of the balance sheet date related to the derivative. For example, the hedged balance on a debt instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DerivativeAmountOfHedgedItem
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

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

- Definition

Foreign exchange rate used to translate amounts denominated in functional currency to reporting currency.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 830
-SubTopic 30
-Section S99
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6897108&loc=SL6897125-166521

+ Details

Name:	us-gaap_ForeignCurrencyExchangeRateTranslation1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis=us-gaap_NetInvestmentHedgingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_HedgingDesignationAxis=us-gaap_DesignatedAsHedgingInstrumentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Financial Risk Management - Market Risk (Details) $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($) CAD / shares CAD / $	Oct. 14, 2016 CAD / $	Oct. 13, 2016 CAD / $	Dec. 31, 2015 USD ($) CAD / $
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Foreign exchange rate (CAD per USD) \| CAD / $	1.34	1.32	1.32	1.38
Estimated effect of 5% change in exchange rate on EPS \| CAD / shares	CAD 0.07
Foreign net investments
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Amount remaining to be hedged	CAD 7,250			$ 3,137
Designated as hedging instrument \| Foreign net investments
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative, Amount of Hedged Item	CAD 3,511			$ 1,535