Goodwill (Details) - Quant & Solutions - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Goodwill [Roll Forward]
Goodwill gross, beginning balance	$ 22.1	$ 22.1
Accumulated impairment, beginning balance	(1.8)	(1.8)
Goodwill, beginning balance	20.3	20.3
Additions	0.0	0.0
Impairments	0.0	0.0
Goodwill gross, ending balance	22.1	22.1
Accumulated impairment, ending balance	(1.8)	(1.8)
Goodwill, ending balance	$ 20.3	$ 20.3