The cash outflow associated with the acquisition of or advances to an entity that is related to it but not strictly controlled (for example, an unconsolidated subsidiary, affiliate, and joint venture or equity method investment) or the acquisition of an additional interest in a subsidiary (controlled entity).

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Subsequent Events (Details) - Upsilon RFO Re Ltd. - Primary Beneficiary - USD ($) $ in Millions			12 Months Ended
	Jan. 01, 2019	Dec. 31, 2018	Dec. 31, 2018	Dec. 30, 2018	Dec. 31, 2017
Non-voting preference shares
Subsequent Event [Line Items]
Investment in variable interest entity			$ 109.8		$ 27.2
Investor \| Non-voting preference shares
Subsequent Event [Line Items]
Investment in variable interest entity			$ 856.7	$ 400.0	$ 7.5
RenaissanceRe Holdings Ltd.
Subsequent Event [Line Items]
Variable interest entity, ownership percentage			14.00%		20.80%
Subsequent Event \| Non-voting preference shares
Subsequent Event [Line Items]
Investment in variable interest entity	$ 100.0
Subsequent Event \| Investor \| Non-voting preference shares
Subsequent Event [Line Items]
Investment in variable interest entity	$ 456.8
Subsequent Event \| RenaissanceRe Holdings Ltd.
Subsequent Event [Line Items]
Variable interest entity, ownership percentage	16.90%
Other liabilities \| Investor \| Non-voting preference shares
Subsequent Event [Line Items]
Investment in variable interest entity		$ 300.0