v3.26.3
Stockholders' Equity - AOCI (Details) - USD ($)
$ in Millions
3 Months Ended 9 Months Ended
Sep. 30, 2026
Sep. 30, 2025
Sep. 30, 2026
Sep. 30, 2025
Change in accumulated other comprehensive income (loss) rollforward        
Balances     $ 11,883.9  
Balances $ 11,816.3   11,816.3  
Accumulated other comprehensive income (loss)        
Change in accumulated other comprehensive income (loss) rollforward        
Balances (4,065.8) $ (4,713.3) (4,188.4) $ (5,224.8)
Other comprehensive income (loss) during the period, net of adjustments (777.0) 389.4 (745.7) 811.0
Amounts reclassified from AOCI 199.8 17.3 291.1 107.2
Other comprehensive income (loss) (577.2) 406.7 (454.6) 918.2
Balances (4,643.0) (4,306.6) (4,643.0) (4,306.6)
Net unrealized gains (losses) on available-for-sale securities        
Change in accumulated other comprehensive income (loss) rollforward        
Balances (3,611.6) (3,854.6) (3,229.1) (4,692.9)
Other comprehensive income (loss) during the period, net of adjustments (2,361.7) 674.9 (2,828.8) 1,428.8
Amounts reclassified from AOCI 21.0 16.7 105.6 101.1
Other comprehensive income (loss) (2,340.7) 691.6 (2,723.2) 1,529.9
Balances (5,952.3) (3,163.0) (5,952.3) (3,163.0)
Net unrealized gains (losses) on available-for-sale debt securities with allowance for credit losses (11.1) (4.7) (11.1) (4.7)
Net unrealized gains (losses) on derivative instruments        
Change in accumulated other comprehensive income (loss) rollforward        
Balances 0.8 (98.8) (31.9) 51.8
Other comprehensive income (loss) during the period, net of adjustments (82.6) 71.8 (50.1) (77.9)
Amounts reclassified from AOCI (0.1) (2.5) 0.1 (3.4)
Other comprehensive income (loss) (82.7) 69.3 (50.0) (81.3)
Balances (81.9) (29.5) (81.9) (29.5)
Liability for future policy benefits discount rate remeasurement gain (loss)        
Change in accumulated other comprehensive income (loss) rollforward        
Balances 1,273.0 1,105.9 812.5 1,438.2
Other comprehensive income (loss) during the period, net of adjustments 1,710.7 (363.3) 2,171.2 (695.6)
Other comprehensive income (loss) 1,710.7 (363.3) 2,171.2 (695.6)
Balances 2,983.7 742.6 2,983.7 742.6
Market risk benefit nonperformance risk remeasurement gain (loss)        
Change in accumulated other comprehensive income (loss) rollforward        
Balances (12.8) (13.3) (13.4) (15.0)
Other comprehensive income (loss) during the period, net of adjustments 5.9 (4.6) 6.5 (2.9)
Other comprehensive income (loss) 5.9 (4.6) 6.5 (2.9)
Balances (6.9) (17.9) (6.9) (17.9)
Foreign currency translation adjustment        
Change in accumulated other comprehensive income (loss) rollforward        
Balances (1,538.9) (1,627.8) (1,546.6) (1,785.9)
Other comprehensive income (loss) during the period, net of adjustments (49.3) 10.6 (43.0) 168.7
Amounts reclassified from AOCI 177.3   178.7  
Other comprehensive income (loss) 128.0 10.6 135.7 168.7
Balances (1,410.9) (1,617.2) (1,410.9) (1,617.2)
Unrecognized postretirement benefit obligations        
Change in accumulated other comprehensive income (loss) rollforward        
Balances (176.3) (224.7) (179.9) (221.0)
Other comprehensive income (loss) during the period, net of adjustments     (1.5) (10.1)
Amounts reclassified from AOCI 1.6 3.1 6.7 9.5
Other comprehensive income (loss) 1.6 3.1 5.2 (0.6)
Balances $ (174.7) $ (221.6) $ (174.7) $ (221.6)