Income Taxes - Effective Rate Reconciliation (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Tax Contingency [Line Items]
Tax (expense) benefit at the U.S. statutory rate	$ 63.4	$ (135.5)	$ (85.1)
Differences in taxes resulting from:
Non-U.S. earnings, net of foreign taxes	(77.2)	78.4	27.1
Tax rate changes	(11.2)	2.7	(5.7)
State taxes	(6.2)	(8.5)	(17.5)
Member’s surplus contributions	(5.6)	(4.8)	(3.6)
Change in valuation allowance	(2.4)	(29.2)	63.6
Officer compensation	(1.5)	(1.1)	0.0
Withholding tax	(0.3)	(5.0)	(1.6)
Tax exempt interest and dividends	0.2	0.8	1.1
Reorganization	0.0	130.5	0.0
Tax reserve adjustments	0.0	1.9	(0.7)
Other, net	2.2	(9.7)	(6.9)
Total income tax (expense) benefit	(38.6)	20.5	(29.3)
Pre-tax income (loss)	(302.0)	645.2	405.1
Tax Payments and Receipts
Net income tax payments to US	(0.1)	16.2	3.7
Non-US
Differences in taxes resulting from:
Pre-tax income (loss)	$ (319.0)	$ 327.8	$ 100.4