Property and Equipment, Net (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Property, Plant and Equipment [Line Items]
Capital office leases - finance lease asset	$ 8.0		$ 8.0		$ 8.0
Total property and equipment, gross	120.7		120.7		110.3
Accumulated depreciation	(71.0)		(71.0)		(55.8)
Total property and equipment, net	49.7		49.7		54.5
Depreciation	5.9	$ 8.6	17.2	$ 29.0
Computer hardware
Property, Plant and Equipment [Line Items]
Total computer hardware and other property	51.4		51.4		45.1
Leasehold improvements
Property, Plant and Equipment [Line Items]
Total computer hardware and other property	15.8		15.8		16.1
Furniture, fixtures and equipment
Property, Plant and Equipment [Line Items]
Total computer hardware and other property	43.3		43.3		39.0
Other
Property, Plant and Equipment [Line Items]
Total computer hardware and other property	$ 2.2		$ 2.2		$ 2.1