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Investments in Unconsolidated Entities - Narrative (Details) - Tuckerman Capital Fund III, L.P. - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2018	Jun. 30, 2018	Jun. 30, 2017	Sep. 30, 2018	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Schedule of Equity Method Investments [Line Items]
Unrealized investment gains	$ 4.2			$ 8.1
Total net income		$ 31.9	$ 3.2		$ 43.7	$ 7.1
Total assets		$ 61.9			$ 61.9		$ 21.8

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The amount of assets reported by an equity method investment of the entity.

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