Segmented Information - Non-insurance companies (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2024	Dec. 31, 2023
Segmented Information
Revenue	$ 6,682.8	$ 6,614.5
Expenses	(6,470.5)	(6,568.7)
Interest and dividends	2,341.9	1,681.6
Share of profit (loss) of associates	956.3	1,022.2
Operating income (loss)	6,683.0	5,707.4
Cost of sales	4,145.6	4,059.6
Non-insurance companies
Segmented Information
Revenue	6,682.8	6,614.5
Expenses	(6,470.5)	(6,568.7)
Interest and dividends	(9.1)	(76.1)
Share of profit (loss) of associates	898.6	941.5
Operating income (loss)	241.4	121.9
Operating segments \| Non-insurance companies
Segmented Information
Revenue	6,682.8	6,614.5
Expenses	(6,470.5)	(6,568.7)
Pre-tax income (loss) before interest expense and other	212.3	45.8
Interest and dividends	(9.1)	(76.1)
Share of profit (loss) of associates	38.2	152.2
Operating income (loss)	241.4	121.9
Operating segments \| Non-insurance companies \| Restaurants and retail
Segmented Information
Revenue	1,953.9	1,772.3
Expenses	(1,797.9)	(1,690.7)
Pre-tax income (loss) before interest expense and other	156.0	81.6
Interest and dividends	10.0	9.9
Share of profit (loss) of associates	0.1
Operating income (loss)	166.1	91.5
Operating segments \| Non-insurance companies \| Fairfax India
Segmented Information
Revenue	319.2	263.3
Expenses	(281.9)	(251.4)
Pre-tax income (loss) before interest expense and other	37.3	11.9
Interest and dividends	(21.3)	(87.4)
Share of profit (loss) of associates	39.0	151.1
Operating income (loss)	55.0	75.6
Operating segments \| Non-insurance companies \| Thomas Cook India
Segmented Information
Revenue	973.4	941.6
Expenses	(929.3)	(906.5)
Pre-tax income (loss) before interest expense and other	44.1	35.1
Share of profit (loss) of associates	0.5	(0.1)
Operating income (loss)	44.6	35.0
Operating segments \| Non-insurance companies \| Other
Segmented Information
Revenue	3,436.3	3,637.3
Expenses	(3,461.4)	(3,720.1)
Pre-tax income (loss) before interest expense and other	(25.1)	(82.8)
Interest and dividends	2.2	1.4
Share of profit (loss) of associates	(1.4)	1.2
Operating income (loss)	$ (24.3)	$ (80.2)

The amount of income arising from interest and dividends, net of adjustments.

No definition available.

Name:	ffh_InterestAndDividendIncomeNetOfAdjustments
Namespace Prefix:	ffh_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The amount of non-insurance expenses.

+ References

No definition available.

+ Details

Name:	ffh_NonInsuranceExpenses
Namespace Prefix:	ffh_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The amount of non-insurance revenues.

+ References

No definition available.

+ Details

Name:	ffh_NonInsuranceRevenues
Namespace Prefix:	ffh_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The amount of non-insurance revenues, net of non-insurance expenses.

+ References

No definition available.

+ Details

Name:	ffh_NonInsuranceRevenuesExpenses
Namespace Prefix:	ffh_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The amount of all expenses directly or indirectly attributed to the goods or services sold. Attributed expenses include, but are not limited to, costs previously included in the measurement of inventory that has now been sold, such as depreciation and maintenance of factory buildings and equipment used in the production process, unallocated production overheads, and abnormal amounts of production costs of inventories.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 1
-IssueDate 2024-01-01
-Paragraph 99
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=1&code=ifrs-tx-2024-en-r&anchor=para_99&doctype=Standard
-URIDate 2024-03-27

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 1
-IssueDate 2024-01-01
-Paragraph 103
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=1&code=ifrs-tx-2024-en-r&anchor=para_103&doctype=Standard
-URIDate 2024-03-27

+ Details

Name:	ifrs-full_CostOfSales
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

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

- Definition

The profit (loss) from operating activities of the entity. [Refer: Profit (loss)]

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 1
-IssueDate 2024-01-01
-Paragraph 85
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=1&code=ifrs-tx-2024-en-r&anchor=para_85&doctype=Standard
-URIDate 2024-03-27

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Name IAS
-Number 32
-IssueDate 2024-01-01
-Paragraph IE33
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=32&code=ifrs-tx-2024-en-r&anchor=para_IE33&doctype=Illustrative%20Examples
-URIDate 2024-03-27

+ Details

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

- Definition

The entity's share of the profit (loss) of associates accounted for using the equity method. [Refer: Total for all associates [member]; Investments accounted for using equity method; Profit (loss)]

+ References

+ Details

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

- Details

Name:	ifrs-full_SegmentsAxis=ffh_SegmentNonInsuranceMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_SegmentConsolidationItemsAxis=ifrs-full_OperatingSegmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ffh_Subsegments1Axis=ffh_RestaurantsAndRetailMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ffh_Subsegments1Axis=ffh_FairfaxIndiaMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ffh_Subsegments1Axis=ffh_ThomasCookIndiaMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ffh_Subsegments1Axis=ffh_OtherSubsegmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: