v3.26.3
Long-Duration Insurance Contracts - Account Balances by Guaranteed Minimum Interest Rates (Details)
$ in Millions
Sep. 30, 2026
USD ($)
Dec. 31, 2025
USD ($)
Policyholder Account Balance [Line Items]    
Policyholders' account balances $ 5,043.2 $ 5,064.1
Less than 2%    
Policyholder Account Balance [Line Items]    
Policyholders' account balances $ 691.6 $ 727.1
Less than 2% | Maximum    
Policyholder Account Balance [Line Items]    
Policyholder account balance, guaranteed minimum credit rating 2.00% 2.00%
Equal to 2% but less than 3%    
Policyholder Account Balance [Line Items]    
Policyholders' account balances $ 579.3 $ 498.8
Equal to 2% but less than 3% | Minimum    
Policyholder Account Balance [Line Items]    
Policyholder account balance, guaranteed minimum credit rating 2.00% 2.00%
Equal to 2% but less than 3% | Maximum    
Policyholder Account Balance [Line Items]    
Policyholder account balance, guaranteed minimum credit rating 3.00% 3.00%
Equal to 3% but less than 4%    
Policyholder Account Balance [Line Items]    
Policyholders' account balances $ 706.1 $ 725.4
Equal to 3% but less than 4% | Minimum    
Policyholder Account Balance [Line Items]    
Policyholder account balance, guaranteed minimum credit rating 3.00% 3.00%
Equal to 3% but less than 4% | Maximum    
Policyholder Account Balance [Line Items]    
Policyholder account balance, guaranteed minimum credit rating 4.00% 4.00%
Equal to 4% but less than 5%    
Policyholder Account Balance [Line Items]    
Policyholders' account balances $ 2,488.6 $ 2,528.1
Equal to 4% but less than 5% | Minimum    
Policyholder Account Balance [Line Items]    
Policyholder account balance, guaranteed minimum credit rating 4.00% 4.00%
Equal to 4% but less than 5% | Maximum    
Policyholder Account Balance [Line Items]    
Policyholder account balance, guaranteed minimum credit rating 5.00% 5.00%
5% or higher    
Policyholder Account Balance [Line Items]    
Policyholders' account balances $ 75.1 $ 78.1
5% or higher | Minimum    
Policyholder Account Balance [Line Items]    
Policyholder account balance, guaranteed minimum credit rating 5.00% 5.00%
Policyholder account balance with a guaranteed minimum crediting rate    
Policyholder Account Balance [Line Items]    
Policyholders' account balances $ 4,540.7 $ 4,557.5
At Guaranteed Minimum | Less than 2%    
Policyholder Account Balance [Line Items]    
Policyholders' account balances 5.9 8.3
At Guaranteed Minimum | Equal to 2% but less than 3%    
Policyholder Account Balance [Line Items]    
Policyholders' account balances 39.0 63.8
At Guaranteed Minimum | Equal to 3% but less than 4%    
Policyholder Account Balance [Line Items]    
Policyholders' account balances 516.6 577.6
At Guaranteed Minimum | Equal to 4% but less than 5%    
Policyholder Account Balance [Line Items]    
Policyholders' account balances 2,488.6 2,528.1
At Guaranteed Minimum | 5% or higher    
Policyholder Account Balance [Line Items]    
Policyholders' account balances 75.1 78.1
At Guaranteed Minimum | Policyholder account balance with a guaranteed minimum crediting rate    
Policyholder Account Balance [Line Items]    
Policyholders' account balances $ 3,125.2 $ 3,255.9
1-50 Basis Points Above | Minimum    
Policyholder Account Balance [Line Items]    
Policyholder account balance, above guaranteed minimum crediting rate 0.0001 0.0001
1-50 Basis Points Above | Maximum    
Policyholder Account Balance [Line Items]    
Policyholder account balance, above guaranteed minimum crediting rate 0.0050 0.0050
1-50 Basis Points Above | Less than 2%    
Policyholder Account Balance [Line Items]    
Policyholders' account balances $ 4.5 $ 10.0
1-50 Basis Points Above | Equal to 2% but less than 3%    
Policyholder Account Balance [Line Items]    
Policyholders' account balances 169.3 142.4
1-50 Basis Points Above | Equal to 3% but less than 4%    
Policyholder Account Balance [Line Items]    
Policyholders' account balances 51.8 10.4
1-50 Basis Points Above | Equal to 4% but less than 5%    
Policyholder Account Balance [Line Items]    
Policyholders' account balances 0.0 0.0
1-50 Basis Points Above | 5% or higher    
Policyholder Account Balance [Line Items]    
Policyholders' account balances 0.0 0.0
1-50 Basis Points Above | Policyholder account balance with a guaranteed minimum crediting rate    
Policyholder Account Balance [Line Items]    
Policyholders' account balances $ 225.6 $ 162.8
51-150 Basis Points Above | Minimum    
Policyholder Account Balance [Line Items]    
Policyholder account balance, above guaranteed minimum crediting rate 0.0051 0.0051
51-150 Basis Points Above | Maximum    
Policyholder Account Balance [Line Items]    
Policyholder account balance, above guaranteed minimum crediting rate 0.0150 0.0150
51-150 Basis Points Above | Less than 2%    
Policyholder Account Balance [Line Items]    
Policyholders' account balances $ 166.6 $ 255.2
51-150 Basis Points Above | Equal to 2% but less than 3%    
Policyholder Account Balance [Line Items]    
Policyholders' account balances 169.6 127.4
51-150 Basis Points Above | Equal to 3% but less than 4%    
Policyholder Account Balance [Line Items]    
Policyholders' account balances 30.3 31.7
51-150 Basis Points Above | Equal to 4% but less than 5%    
Policyholder Account Balance [Line Items]    
Policyholders' account balances 0.0 0.0
51-150 Basis Points Above | 5% or higher    
Policyholder Account Balance [Line Items]    
Policyholders' account balances 0.0 0.0
51-150 Basis Points Above | Policyholder account balance with a guaranteed minimum crediting rate    
Policyholder Account Balance [Line Items]    
Policyholders' account balances $ 366.5 $ 414.3
Greater Than 150 Basis Points Above | Minimum    
Policyholder Account Balance [Line Items]    
Policyholder account balance, above guaranteed minimum crediting rate 0.0150 0.0150
Greater Than 150 Basis Points Above | Less than 2%    
Policyholder Account Balance [Line Items]    
Policyholders' account balances $ 514.7 $ 453.6
Greater Than 150 Basis Points Above | Equal to 2% but less than 3%    
Policyholder Account Balance [Line Items]    
Policyholders' account balances 201.5 165.1
Greater Than 150 Basis Points Above | Equal to 3% but less than 4%    
Policyholder Account Balance [Line Items]    
Policyholders' account balances 107.4 105.8
Greater Than 150 Basis Points Above | Equal to 4% but less than 5%    
Policyholder Account Balance [Line Items]    
Policyholders' account balances 0.0 0.0
Greater Than 150 Basis Points Above | 5% or higher    
Policyholder Account Balance [Line Items]    
Policyholders' account balances 0.0 0.0
Greater Than 150 Basis Points Above | Policyholder account balance with a guaranteed minimum crediting rate    
Policyholder Account Balance [Line Items]    
Policyholders' account balances $ 823.6 $ 724.5