Reserves (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Jun. 30, 2023	Dec. 31, 2020
Liability for Claims and Claims Adjustment Expense [Line Items]
Interest expense (original discount rate)	5.95%	5.95%			5.95%
Current discount rate	6.01%	5.52%			1.69%
Unfavorable (favorable) prior year development	$ (26.6)	$ 55.5	$ (11.6)
Retroactive reinsurance treaty, coverage limit				$ 50.0
Non-core Operations | Corporate and Other
Liability for Claims and Claims Adjustment Expense [Line Items]
Unfavorable (favorable) prior year development	40.1	77.4	23.3
Small Commercial Insurance | Corporate and Other
Liability for Claims and Claims Adjustment Expense [Line Items]
Unfavorable (favorable) prior year development	(0.5)	15.3	16.2
Sharing Economy Insurance Product | Corporate and Other
Liability for Claims and Claims Adjustment Expense [Line Items]
Unfavorable (favorable) prior year development	40.6	62.1	7.1
Global Lifestyle
Liability for Claims and Claims Adjustment Expense [Line Items]
Prior year development of claims and benefits payable, foreign exchange rate impact	0.3	(0.4)	(0.7)
Global Lifestyle | Operating Segments
Liability for Claims and Claims Adjustment Expense [Line Items]
Unfavorable (favorable) prior year development	(23.6)	(45.4)	(32.9)
Global Lifestyle | Connected Living | Operating Segments
Liability for Claims and Claims Adjustment Expense [Line Items]
Unfavorable (favorable) prior year development	(26.2)
Global Lifestyle | Financial Service | Operating Segments
Liability for Claims and Claims Adjustment Expense [Line Items]
Unfavorable (favorable) prior year development	(14.7)
Global Lifestyle | Mobile Service | Operating Segments
Liability for Claims and Claims Adjustment Expense [Line Items]
Unfavorable (favorable) prior year development	(6.0)
Global Lifestyle | Extended Service Contract | Operating Segments
Liability for Claims and Claims Adjustment Expense [Line Items]
Unfavorable (favorable) prior year development	(5.5)
Global Lifestyle | Global Automotive | Operating Segments
Liability for Claims and Claims Adjustment Expense [Line Items]
Unfavorable (favorable) prior year development	2.7
Global Housing | Operating Segments
Liability for Claims and Claims Adjustment Expense [Line Items]
Unfavorable (favorable) prior year development	$ (37.1)	$ 28.9	$ 6.7