Investments - Investments in Equity Securities (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Equity Securities
Beginning balance	$ 96.5	$ 77.8
New investments	8.7	9.4
Decrease in fair value of investments in equity securities	(14.4)	13.1
Foreign currency translation adjustments and other	0.4	(3.8)
Ending balance	91.2	96.5
Investment in Equity Securities Level 1
Equity Securities
Beginning balance	17.2	31.3
New investments	0.0	0.0
Decrease in fair value of investments in equity securities	(12.7)	(11.8)
Foreign currency translation adjustments and other	0.3	(2.3)
Ending balance	4.8	17.2
Investment in Equity Securities, Level 2
Equity Securities
Beginning balance	7.8	6.2
New investments	0.0	0.0
Decrease in fair value of investments in equity securities	(1.7)	1.6
Foreign currency translation adjustments and other	0.0	0.0
Ending balance	6.1	7.8
Investments in Equity Securities, All Others
Equity Securities
Beginning balance	71.5	40.3
New investments	8.7	9.4
Decrease in fair value of investments in equity securities	0.0	23.3
Foreign currency translation adjustments and other	0.1	(1.5)
Ending balance	$ 80.3	$ 71.5