Schedule of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Accumulated Other Comprehensive Loss
Balance at Beginning of Period	$ (1,808.5)	$ (2,523.7)
Other Comprehensive Income (Loss) Before Reclassifications	10.1	187.3
Amounts Reclassified from AOCI	(2.9)	(157.6)
Total Other Comprehensive Income	13.0	344.9
Balance at End of Period	(1,795.5)	(2,178.8)
Net Unrealized Loss on Securities
Accumulated Other Comprehensive Loss
Balance at Beginning of Period	(2,003.1)	(2,755.2)
Other Comprehensive Income (Loss) Before Reclassifications	(431.3)	265.6
Amounts Reclassified from AOCI	(2.1)	(156.4)
Total Other Comprehensive Income	(429.2)	422.0
Balance at End of Period	(2,432.3)	(2,333.2)
Effect of Change in Discount Rate Assumptions on the LFPB1
Accumulated Other Comprehensive Loss
Balance at Beginning of Period	929.9	1,185.4
Other Comprehensive Income (Loss) Before Reclassifications	465.2	(166.3)
Amounts Reclassified from AOCI	0.0	0.0
Total Other Comprehensive Income	465.2	(166.3)
Balance at End of Period	1,395.1	1,019.1
Net Loss on Derivatives
Accumulated Other Comprehensive Loss
Balance at Beginning of Period	(278.8)	(270.7)
Other Comprehensive Income (Loss) Before Reclassifications	(2.0)	47.5
Amounts Reclassified from AOCI	1.3	2.0
Total Other Comprehensive Income	(3.3)	45.5
Balance at End of Period	(282.1)	(225.2)
Foreign Currency Translation Adjustment
Accumulated Other Comprehensive Loss
Balance at Beginning of Period	(245.6)	(343.0)
Other Comprehensive Income (Loss) Before Reclassifications	(23.0)	42.3
Amounts Reclassified from AOCI	0.0	0.0
Total Other Comprehensive Income	(23.0)	42.3
Balance at End of Period	(268.6)	(300.7)
Unrecognized Pension and Postretirement Benefit Costs
Accumulated Other Comprehensive Loss
Balance at Beginning of Period	(210.9)	(340.2)
Other Comprehensive Income (Loss) Before Reclassifications	1.2	(1.8)
Amounts Reclassified from AOCI	(2.1)	(3.2)
Total Other Comprehensive Income	3.3	1.4
Balance at End of Period	$ (207.6)	$ (338.8)