Schedule of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Accumulated Other Comprehensive Income (Loss)
Balance at Beginning of Period	$ (3,457.6)	$ (3,809.5)	$ (3,448.3)	$ (5,164.6)
Other Comprehensive Income (Loss) Before Reclassifications	282.8	194.2	278.0	1,551.7
Amounts Reclassified from Accumulated Other Comprehensive Income or Loss	(24.2)	(4.3)	(19.7)	(1.9)
Net Other Comprehensive Income (Loss)	307.0	198.5	297.7	1,553.6
Balance at End of Period	(3,150.6)	(3,611.0)	(3,150.6)	(3,611.0)
Net Unrealized Gain (Loss) on Securities
Accumulated Other Comprehensive Income (Loss)
Balance at Beginning of Period	(2,762.6)	(1,560.4)	(3,028.4)	4,014.4
Other Comprehensive Income (Loss) Before Reclassifications	(1,215.1)	(1,937.0)	(957.2)	(7,524.6)
Amounts Reclassified from Accumulated Other Comprehensive Income or Loss	(29.3)	(11.1)	(37.2)	(23.9)
Net Other Comprehensive Income (Loss)	(1,185.8)	(1,925.9)	(920.0)	(7,500.7)
Balance at End of Period	(3,948.4)	(3,486.3)	(3,948.4)	(3,486.3)
Effect of Change in Discount Rate Assumptions on the LFPB
Accumulated Other Comprehensive Income (Loss)
Balance at Beginning of Period	0.1	(1,541.2)	313.9	(8,570.7)
Other Comprehensive Income (Loss) Before Reclassifications	1,688.4	2,222.9	1,374.6	9,252.4
Amounts Reclassified from Accumulated Other Comprehensive Income or Loss	0.0	0.0	0.0	0.0
Net Other Comprehensive Income (Loss)	1,688.4	2,222.9	1,374.6	9,252.4
Balance at End of Period	1,688.5	681.7	1,688.5	681.7
Net Gain (Loss) on Hedges
Accumulated Other Comprehensive Income (Loss)
Balance at Beginning of Period	(33.3)	46.4	(9.6)	61.8
Other Comprehensive Income (Loss) Before Reclassifications	(137.9)	(23.0)	(146.4)	(17.1)
Amounts Reclassified from Accumulated Other Comprehensive Income or Loss	6.5	9.9	21.7	31.2
Net Other Comprehensive Income (Loss)	(144.4)	(32.9)	(168.1)	(48.3)
Balance at End of Period	(177.7)	13.5	(177.7)	13.5
Foreign Currency Translation Adjustment
Accumulated Other Comprehensive Income (Loss)
Balance at Beginning of Period	(327.1)	(367.5)	(390.1)	(274.1)
Other Comprehensive Income (Loss) Before Reclassifications	(55.1)	(71.5)	7.9	(164.9)
Amounts Reclassified from Accumulated Other Comprehensive Income or Loss	0.0	0.0	0.0	0.0
Net Other Comprehensive Income (Loss)	(55.1)	(71.5)	7.9	(164.9)
Balance at End of Period	(382.2)	(439.0)	(382.2)	(439.0)
Unrecognized Pension and Postretirement Benefit Costs
Accumulated Other Comprehensive Income (Loss)
Balance at Beginning of Period	(334.7)	(386.8)	(334.1)	(396.0)
Other Comprehensive Income (Loss) Before Reclassifications	2.5	2.8	(0.9)	5.9
Amounts Reclassified from Accumulated Other Comprehensive Income or Loss	(1.4)	(3.1)	(4.2)	(9.2)
Net Other Comprehensive Income (Loss)	3.9	5.9	3.3	15.1
Balance at End of Period	$ (330.8)	$ (380.9)	$ (330.8)	$ (380.9)