v3.26.1
Other Comprehensive (Loss) Income and Accumulated Other Comprehensive Loss (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
AOCI Attributable to Parent, Net of Tax [Roll Forward]        
Equity, Attributable to Parent, Beginning Balance     $ 2,681.4  
Other Comprehensive (Loss) Income Net of Tax Expense (Benefit) $ 21.3 $ 3.8 0.6 $ 47.0
Equity, Attributable to Parent, Ending Balance 2,192.8   2,192.8  
Accumulated Other Comprehensive Loss        
AOCI Attributable to Parent, Net of Tax [Roll Forward]        
Equity, Attributable to Parent, Beginning Balance (226.7) (261.3) (206.2) (304.5)
Other Comprehensive (Loss) Income Before Reclassifications 23.3 7.7 2.1 51.3
Amounts Reclassified from AOCI Net of Tax Expense (Benefit) (1.9) (4.1) (1.2) (4.5)
Other Comprehensive (Loss) Income Net of Tax Expense (Benefit) 21.4 3.6 0.9 46.8
Equity, Attributable to Parent, Ending Balance (205.3) (257.7) (205.3) (257.7)
Amounts Reclassified from AOCI, Tax Expense (Benefit) (0.4) (1.2) (0.2) (1.3)
Other Comprehensive (Loss) Income, Tax Expense (Benefit) 5.9 1.0 0.4 (11.8)
Having No Credit Losses Recognized in Condensed Consolidated Statements of Income        
AOCI Attributable to Parent, Net of Tax [Roll Forward]        
Equity, Attributable to Parent, Beginning Balance (628.9) (633.1) (559.5) (687.8)
Other Comprehensive (Loss) Income Before Reclassifications 40.3 2.8 (30.2) 56.0
Amounts Reclassified from AOCI Net of Tax Expense (Benefit) (0.4) (1.4) 0.7 0.1
Other Comprehensive (Loss) Income Net of Tax Expense (Benefit) 39.9 1.4 (29.5) 56.1
Equity, Attributable to Parent, Ending Balance (589.0) (631.7) (589.0) (631.7)
Amounts Reclassified from AOCI, Tax Expense (Benefit) (0.1) (0.4) 0.2 0.0
Other Comprehensive (Loss) Income, Tax Expense (Benefit) 10.7 0.4 (7.8) (14.9)
Having Credit Losses Recognized in Condensed Consolidated Statements of Income        
AOCI Attributable to Parent, Net of Tax [Roll Forward]        
Equity, Attributable to Parent, Beginning Balance (4.0) (2.2) (3.0) (3.2)
Other Comprehensive (Loss) Income Before Reclassifications 1.4 2.5 0.4 4.8
Amounts Reclassified from AOCI Net of Tax Expense (Benefit) (1.1) (2.5) (1.1) (3.8)
Other Comprehensive (Loss) Income Net of Tax Expense (Benefit) 0.3 0.0 (0.7) 1.0
Equity, Attributable to Parent, Ending Balance (3.7) (2.2) (3.7) (2.2)
Amounts Reclassified from AOCI, Tax Expense (Benefit) (0.3) (0.7) (0.3) (1.0)
Other Comprehensive (Loss) Income, Tax Expense (Benefit) 0.1 0.0 (0.2) (0.3)
Net Unrecognized Postretirement Benefit Income        
AOCI Attributable to Parent, Net of Tax [Roll Forward]        
Equity, Attributable to Parent, Beginning Balance 5.8 8.0 6.1 8.4
Other Comprehensive (Loss) Income Before Reclassifications 0.0 0.0 0.0 0.0
Amounts Reclassified from AOCI Net of Tax Expense (Benefit) (0.3) (0.4) (0.6) (0.8)
Other Comprehensive (Loss) Income Net of Tax Expense (Benefit) (0.3) (0.4) (0.6) (0.8)
Equity, Attributable to Parent, Ending Balance 5.5 7.6 5.5 7.6
Amounts Reclassified from AOCI, Tax Expense (Benefit) 0.0 (0.2) (0.1) (0.3)
Other Comprehensive (Loss) Income, Tax Expense (Benefit) 0.0 (0.2) (0.1) 0.3
Net Loss on Cash Flow Hedges        
AOCI Attributable to Parent, Net of Tax [Roll Forward]        
Equity, Attributable to Parent, Beginning Balance (0.7) 0.0 (0.6) (2.2)
Other Comprehensive (Loss) Income Before Reclassifications 0.0 (1.6) 0.0 0.8
Amounts Reclassified from AOCI Net of Tax Expense (Benefit) (0.1) 0.2 (0.2) 0.0
Other Comprehensive (Loss) Income Net of Tax Expense (Benefit) (0.1) (1.4) (0.2) 0.8
Equity, Attributable to Parent, Ending Balance (0.8) (1.4) (0.8) (1.4)
Amounts Reclassified from AOCI, Tax Expense (Benefit) 0.0 0.1 0.0 0.0
Other Comprehensive (Loss) Income, Tax Expense (Benefit) 0.0 (0.3) 0.0 0.4
Change in Discount Rate on Future Life Policyholder Benefits        
AOCI Attributable to Parent, Net of Tax [Roll Forward]        
Equity, Attributable to Parent, Beginning Balance 401.1 366.0 350.8 380.3
Other Comprehensive (Loss) Income Before Reclassifications (18.4) 4.0 31.9 (10.3)
Amounts Reclassified from AOCI Net of Tax Expense (Benefit) 0.0 0.0 0.0 0.0
Other Comprehensive (Loss) Income Net of Tax Expense (Benefit) (18.4) 4.0 31.9 (10.3)
Equity, Attributable to Parent, Ending Balance 382.7 370.0 382.7 370.0
Amounts Reclassified from AOCI, Tax Expense (Benefit) 0.0 0.0 0.0 0.0
Other Comprehensive (Loss) Income, Tax Expense (Benefit) $ (4.9) $ 1.1 $ 8.5 $ 2.7