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Other Investments - Investments Measured at NAV as a Practical Expedient (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2024	Dec. 31, 2023
NAV of investments at fair value
Unfunded Commitments	$ 217.5	$ 187.2
Life of funds (generally up to)	15 years
Private equity funds
NAV of investments at fair value
Unfunded Commitments	$ 217.5	187.2
Investments in other strategies
NAV of investments at fair value
Unfunded Commitments	0.0	0.0
Fair Value Measured at NAV
NAV of investments at fair value
Fair Value	479.9	430.5
Fair Value Measured at NAV | Controlling Interest
NAV of investments at fair value
Fair Value	361.4	324.9
Fair Value Measured at NAV | Private equity funds
NAV of investments at fair value
Fair Value	473.1	424.4
Fair Value Measured at NAV | Investments in other strategies
NAV of investments at fair value
Fair Value	$ 6.8	$ 6.1

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