SEGMENT INFORMATION - Reportable Segment Revenue, Income (Loss) Before Income Taxes, (Provision) Benefit for Income Taxes and Net Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Segment Reporting Information
Total revenues	$ 4,470.5	$ 4,130.0
Income before income taxes	193.3	206.4
U.S.
Segment Reporting Information
Total revenues	3,645.7	3,342.4
Income before income taxes	180.0	180.7
U.K.
Segment Reporting Information
Total revenues	824.8	787.7
Income before income taxes	$ 13.3	$ 25.7