Earnings per Share (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Earnings per share [abstract]
Net earnings attributable to shareholders of Fairfax	$ 376.0	$ 1,740.6
Preferred share dividends	(45.1)	(44.6)
Net earnings attributable to common shareholders – basic and diluted	$ 330.9	$ 1,696.0
Weighted average common shares outstanding – basic (in shares)	27,505,896	25,411,246
Share-based payment awards (in shares)	890,985	689,571
Weighted average common shares outstanding – diluted (in shares)	28,396,881	26,100,817
Net earnings per common share – basic (in dollars per share)	$ 12.03	$ 66.74
Net earnings per common share – diluted (in dollars per share)	$ 11.65	$ 64.98

The weighted average number of ordinary shares outstanding plus the weighted average number of ordinary shares that would be issued on the conversion of all the dilutive potential ordinary shares into ordinary shares. [Refer: Ordinary shares [member]; Weighted average [member]]

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Adjustment to profit (loss) for preference share dividends to calculate profit (loss) attributable to ordinary equity holders of the parent equity. [Refer: Preference shares [member]; Profit (loss)]

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The amount of profit (loss) attributable to ordinary equity holders of the parent entity (the numerator) divided by the weighted average number of ordinary shares outstanding during the period (the denominator).

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The amount of profit (loss) attributable to ordinary equity holders of the parent entity (the numerator), divided by the weighted average number of ordinary shares outstanding during the period (the denominator), both adjusted for the effects of all dilutive potential ordinary shares. [Refer: Ordinary shares [member]; Weighted average [member]]

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The number of dilutive potential ordinary shares that relate to the assumed exercise of the entity's share options.

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The profit (loss) attributable to ordinary equity holders of the parent equity, adjusted for the effects of all dilutive potential ordinary shares. [Refer: Profit (loss)]

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The profit (loss) from continuing and discontinued operations attributable to owners of the parent. [Refer: Profit (loss)]

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The number of ordinary shares outstanding at the beginning of the period, adjusted by the number of ordinary shares bought back or issued during the period multiplied by a time-weighting factor.

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