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Significant Transactions - Ark (Details) - USD ($) $ in Millions		3 Months Ended	12 Months Ended
	Oct. 01, 2020	Mar. 31, 2021	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Sep. 30, 2021	Jan. 01, 2021	Dec. 31, 2020
Other Significant Noncash Transactions [Line Items]
Cash pre-funded/placed in escrow for Ark Transaction								$ 646.3
Change in fair value of contingent consideration - Ark			$ 48.7	$ 17.3	$ 5.5
Other Operations
Other Significant Noncash Transactions [Line Items]
Cash pre-funded/placed in escrow for Ark Transaction								366.3
Change in fair value of contingent consideration - Ark			$ 0.0	0.0	0.0
Ark
Other Significant Noncash Transactions [Line Items]
Basic ownership							72.00%
Ownership percentage, after equity incentives							63.00%
Percent of shares outstanding			12.50%
Subordinated Debt | Ark 2021 Subordinated Notes
Other Significant Noncash Transactions [Line Items]
Long-term line of credit						$ 163.3
Ark | Lloyd
Other Significant Noncash Transactions [Line Items]
Cash pre-funded/placed in escrow for Ark Transaction								$ 280.0
Ark
Other Significant Noncash Transactions [Line Items]
Merger agreement, equity capital contributed	$ 605.4
Equity capital, pre money valuation amount	300.0
Additional equity purchase from shareholders	40.9
Investment, potential additional contribution of equity capital	$ 200.0						$ 200.0
Percent of shares outstanding			12.50%
Assets acquired							2,500.0
Goodwill and intangible assets acquired							292.5
Liabilities acquired							1,700.0
Contingent consideration			$ 94.0	45.3			22.5
Noncontrolling interest acquired							$ 220.2
Transaction costs		$ 25.3
Amortization			0.0	7.5	64.2
Change in fair value of contingent consideration - Ark			$ 48.7	$ 17.3	$ 5.5

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