Segment Information - Schedule of Net Earned Premiums by Segment and Product (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Global Lifestyle
Segment Reporting Information [Line Items]
Net earned premiums, fees and other income	$ 2,249.5	$ 2,105.8	$ 6,620.8	$ 6,255.0
Global Lifestyle | Connected Living
Segment Reporting Information [Line Items]
Net earned premiums, fees and other income	1,223.5	1,082.9	3,512.3	3,188.7
Global Lifestyle | Global Automotive
Segment Reporting Information [Line Items]
Net earned premiums, fees and other income	1,026.0	1,022.9	3,108.5	3,066.3
Global Housing
Segment Reporting Information [Line Items]
Net earned premiums, fees and other income	603.8	555.2	1,809.6	1,597.1
Global Housing | Homeowners
Segment Reporting Information [Line Items]
Net earned premiums, fees and other income	478.4	434.1	1,438.5	1,237.8
Global Housing | Renters and Other
Segment Reporting Information [Line Items]
Net earned premiums, fees and other income	$ 125.4	$ 121.1	$ 371.1	$ 359.3