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Income Taxes - Effective Rate Reconciliation (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Income Tax Contingency [Line Items]
Tax (expense) benefit at the U.S. statutory rate	$ 31.4	$ 57.5	$ (138.7)
Differences in taxes resulting from:
Non-U.S. earnings, net of foreign taxes	(41.2)	(78.2)	74.3
Change in valuation allowance	(19.6)	(2.0)	(26.6)
Member’s surplus contributions	(6.2)	(5.6)	(4.8)
Withholding tax	(3.1)	(0.3)	(5.0)
State taxes	(2.8)	(7.3)	(8.9)
Officer compensation	(1.0)	(1.5)	(1.1)
Tax rate changes	(0.4)	(10.9)	3.1
Tax exempt interest and dividends	0.2	0.2	0.8
Reorganization	0.0	0.0	130.5
Tax reserve adjustments	0.0	0.0	1.9
Other, net	1.3	3.7	(10.7)
Total income tax (expense) benefit	(41.4)	(44.4)	14.8
Pre-tax income (loss)	(149.4)	(273.6)	660.4
Tax Payments and Receipts
Net income tax payments to US	10.3	(0.1)	15.9
Non-US
Differences in taxes resulting from:
Pre-tax income (loss)	$ (94.4)	$ (319.0)	$ 327.8

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