Acquisitions and Divestitures - Acquisition of Peak Achievement Athletics Inc. (Details) - Peak Achievement Athletics, Inc. - USD ($) $ in Millions		12 Months Ended
Dec. 20, 2024	Dec. 31, 2023
Acquisitions and Divestitures
Percentage equity interest in acquiree	100.00%	42.60%
Purchase consideration	$ 765.0
New non-recourse borrowings	339.0
Fair value of equity interest previously held	325.7
Cash consideration	100.3
Gain on remeasurement of previously held equity interest	$ 203.4
Sagard Holdings Inc.
Acquisitions and Divestitures
Percentage of interests acquired	42.60%
Other Minority Shareholders
Acquisitions and Divestitures
Percentage of interests acquired	14.80%

The amount of new non-recourse borrowings incurred ad purchase consideration in a business acquisition.

No definition available.

Name:	ffh_BusinessAcquisitionNewNonRecourseBorrowings
Namespace Prefix:	ffh_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The fair value at acquisition date of the consideration transferred and the existing equity interest in the acquired entity previously held by the Company.

+ References

No definition available.

+ Details

Name:	ffh_BusinessCombinationPurchaseConsideration
Namespace Prefix:	ffh_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The acquisition-date fair value of equity interest in the acquiree held by the acquirer immediately before the acquisition date in a business combination achieved in stages. [Refer: Total for all business combinations [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 3
-IssueDate 2024-01-01
-Paragraph B64
-Subparagraph p
-Clause i
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=3&code=ifrs-tx-2024-en-r&anchor=para_B64_p_i&doctype=Appendix&subtype=B
-URIDate 2024-03-27

+ Details

Name:	ifrs-full_AcquisitiondateFairValueOfEquityInterestInAcquireeHeldByAcquirerImmediatelyBeforeAcquisitionDate
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The fair value, at acquisition date, of cash transferred as consideration in a business combination. [Refer: Total for all business combinations [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 3
-IssueDate 2024-01-01
-Paragraph B64
-Subparagraph f
-Clause i
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=3&code=ifrs-tx-2024-en-r&anchor=para_B64_f_i&doctype=Appendix&subtype=B
-URIDate 2024-03-27

+ Details

Name:	ifrs-full_CashTransferred
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Line items represent concepts included in a table. These concepts are used to disclose reportable information associated with members defined in one or many axes of the table.

+ References

No definition available.

+ Details

Name:	ifrs-full_DisclosureOfBusinessCombinationsLineItems
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The gain (loss) recognised as result of remeasuring to fair value the equity interest in the acquiree held by the acquirer before the business combination. [Refer: Total for all business combinations [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 3
-IssueDate 2024-01-01
-Paragraph B64
-Subparagraph p
-Clause ii
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=3&code=ifrs-tx-2024-en-r&anchor=para_B64_p_ii&doctype=Appendix&subtype=B
-URIDate 2024-03-27

+ Details

Name:	ifrs-full_GainLossRecognisedAsResultOfRemeasuringToFairValueEquityInterestInAcquireeHeldByAcquirerBeforeBusinessCombination
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The percentage of voting equity interests acquired in a business combination. [Refer: Total for all business combinations [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 3
-IssueDate 2024-01-01
-Paragraph B64
-Subparagraph c
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=3&code=ifrs-tx-2024-en-r&anchor=para_B64_c&doctype=Appendix&subtype=B
-URIDate 2024-03-27

+ Details

Name:	ifrs-full_PercentageOfVotingEquityInterestsAcquired
Namespace Prefix:	ifrs-full_
Data Type:	dtr-2022:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The proportion of ownership interest in a subsidiary attributable to the entity. [Refer: Total for all subsidiaries [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 27
-IssueDate 2024-01-01
-Paragraph 17
-Subparagraph b
-Clause iii
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=27&code=ifrs-tx-2024-en-r&anchor=para_17_b_iii&doctype=Standard
-URIDate 2024-03-27

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 27
-IssueDate 2024-01-01
-Paragraph 16
-Subparagraph b
-Clause iii
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=27&code=ifrs-tx-2024-en-r&anchor=para_16_b_iii&doctype=Standard
-URIDate 2024-03-27

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 12
-IssueDate 2024-01-01
-Paragraph 19B
-Subparagraph c
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=12&code=ifrs-tx-2024-en-r&anchor=para_19B_c&doctype=Standard
-URIDate 2024-03-27

+ Details

Name:	ifrs-full_ProportionOfOwnershipInterestInSubsidiary
Namespace Prefix:	ifrs-full_
Data Type:	dtr-2022:percentItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	ifrs-full_BusinessCombinationsAxis=ffh_PeakAchievementAthleticsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_CounterpartyNameAxis=ffh_SagardHoldingsIncMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_CounterpartyNameAxis=ffh_OtherMinorityShareholdersMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: