Income Taxes - Effective Rate Reconciliation (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Income Tax Disclosure [Abstract]
Tax (expense) benefit at the U.S. statutory rate	$ (66.5)	$ (118.7)	$ 31.4
Differences in taxes resulting from:
Non-U.S. earnings, net of foreign taxes	40.2	103.7	(41.2)
Change in valuation allowance	(8.1)	(30.2)	(19.6)
Bermuda corporate income tax	5.0	68.0	0.0
Noncontrolling interest	3.9	6.8	3.4
Tax rate changes	2.9	(0.6)	(0.4)
BAM member surplus contributions prior to deconsolidation	(2.8)	(5.7)	(6.2)
Withholding tax	(2.5)	(4.1)	(3.1)
State taxes	(1.8)	(8.2)	(2.8)
Tax exempt interest and dividends	0.3	0.2	0.2
Officer compensation	0.0	(0.2)	(1.0)
Other, net	(3.2)	4.5	(2.1)
Total income tax (expense) benefit	$ (32.6)	$ 15.5	$ (41.4)