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Held for Sale and Discontinued Operations - Narrative (Details) - USD ($)		3 Months Ended
	Feb. 12, 2021	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net gain from sale of discontinued operations, net of tax		$ 18,700,000	$ 900,000
(Loss) gain on sale		(28,700,000)
Corporate Aircraft
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Assets Held-for-sale, Not Part of Disposal Group				$ 1,700,000
Proceeds from sale of property held-for-sale	$ 2,100,000
Realized gain on sale of corporate aircraft		500,000
Fresh Insurance Services Group Limited
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from sale of other assets		1,500,000
Discontinued Operations \| Sirius Group
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net gain from sale of discontinued operations, net of tax		17,600,000
Contingent liability				$ 18,700,000
Discontinued Operations \| Sirius Group \| Foreign Currency Gain (Loss)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net gain from sale of discontinued operations, net of tax		$ 1,100,000