v3.25.2
Accumulated Other Comprehensive Income (Loss) (Summary of Changes in Accumulated Other Comprehensive Income (Loss) (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2025
Mar. 31, 2025
Jun. 30, 2024
Mar. 31, 2024
Jun. 30, 2025
Jun. 30, 2024
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]            
Beginning balance $ 12,878.5 $ 12,788.4 $ 12,101.8 $ 11,897.9 $ 12,788.4 $ 11,897.9
Net Change 40.3 74.5 52.6 220.3 114.8 272.9
Ending balance 12,866.5 12,878.5 12,655.8 12,101.8 12,866.5 12,655.8
TOTAL            
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]            
Beginning balance (739.5) (814.0) (917.6) (1,137.9) (814.0) (1,137.9)
Net Change 40.3 74.5 52.6 220.3    
Ending balance (699.2) (739.5) (865.0) (917.6) (699.2) (865.0)
NET UNREALIZED GAINS (LOSSES) ON AVAILABLE FOR SALE DEBT SECURITIES            
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]            
Beginning balance (527.1) (598.1) (710.5) (923.9) (598.1) (923.9)
Net Change 45.9   43.4   116.9 256.8
Ending balance (481.2) (527.1) (667.1) (710.5) (481.2) (667.1)
NET UNREALIZED GAINS (LOSSES) ON CASH FLOW HEDGES            
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]            
Beginning balance 0.1 0.6 0.1 0.8 0.6 0.8
Net Change (0.1)   (0.1)   (0.6) (0.8)
Ending balance 0.0 0.1 0.0 0.1 0.0 0.0
NET FOREIGN CURRENCY ADJUSTMENT            
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]            
Beginning balance 237.8 233.1 208.2 203.6 233.1 203.6
Net Change (7.7)   7.0   (3.0) 11.6
Ending balance 230.1 237.8 215.2 208.2 230.1 215.2
NET PENSION AND OTHER POSTRETIREMENT BENEFIT ADJUSTMENTS            
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]            
Beginning balance (450.3) (449.6) (415.4) (418.4) (449.6) (418.4)
Net Change 2.2   2.3   1.5 5.3
Ending balance $ (448.1) $ (450.3) $ (413.1) $ (415.4) $ (448.1) $ (413.1)