Schedule of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Accumulated Other Comprehensive Income (Loss)
Balance at Beginning of Period	$ (3,308.0)	$ (3,448.3)
Other Comprehensive Income (Loss) Before Reclassifications	356.8	293.1
Amounts Reclassified from Accumulated Other Comprehensive Income or Loss	(11.2)	7.1
Total Other Comprehensive Income	368.0	286.0
Balance at End of Period	(2,940.0)	(3,162.3)
Net Unrealized Loss on Securities
Accumulated Other Comprehensive Income (Loss)
Balance at Beginning of Period	(1,919.1)	(3,028.4)
Other Comprehensive Income (Loss) Before Reclassifications	(454.1)	823.4
Amounts Reclassified from Accumulated Other Comprehensive Income or Loss	(12.4)	0.2
Total Other Comprehensive Income	(441.7)	823.2
Balance at End of Period	(2,360.8)	(2,205.2)
Effect of Change in Discount Rate Assumptions on the LFPB1
Accumulated Other Comprehensive Income (Loss)
Balance at Beginning of Period	(648.4)	313.9
Other Comprehensive Income (Loss) Before Reclassifications	873.7	(573.9)
Amounts Reclassified from Accumulated Other Comprehensive Income or Loss	0.0	0.0
Total Other Comprehensive Income	873.7	(573.9)
Balance at End of Period	225.3	(260.0)
Net Gain (Loss) on Derivatives
Accumulated Other Comprehensive Income (Loss)
Balance at Beginning of Period	(73.7)	(9.6)
Other Comprehensive Income (Loss) Before Reclassifications	(48.9)	25.6
Amounts Reclassified from Accumulated Other Comprehensive Income or Loss	4.4	8.2
Total Other Comprehensive Income	(53.3)	17.4
Balance at End of Period	(127.0)	7.8
Foreign Currency Translation Adjustment
Accumulated Other Comprehensive Income (Loss)
Balance at Beginning of Period	(321.1)	(390.1)
Other Comprehensive Income (Loss) Before Reclassifications	(11.5)	24.7
Amounts Reclassified from Accumulated Other Comprehensive Income or Loss	0.0	0.0
Total Other Comprehensive Income	(11.5)	24.7
Balance at End of Period	(332.6)	(365.4)
Unrecognized Pension and Postretirement Benefit Costs
Accumulated Other Comprehensive Income (Loss)
Balance at Beginning of Period	(345.7)	(334.1)
Other Comprehensive Income (Loss) Before Reclassifications	(2.4)	(6.7)
Amounts Reclassified from Accumulated Other Comprehensive Income or Loss	(3.2)	(1.3)
Total Other Comprehensive Income	0.8	(5.4)
Balance at End of Period	$ (344.9)	$ (339.5)