v3.26.1
Investment Securities - Fair Value of Hedge Funds Subject to Restrictions on Redemption Frequency (Details) - USD ($)
$ in Millions
Jun. 30, 2026
Dec. 31, 2025
Debt and Equity Securities, FV-NI [Line Items]    
Unfunded Commitments $ 91.0 $ 65.8
Total private equity funds and hedge funds    
Debt and Equity Securities, FV-NI [Line Items]    
Fair Value 479.5 395.2
Unfunded Commitments 91.0 65.8
Private equity funds    
Debt and Equity Securities, FV-NI [Line Items]    
Fair Value 248.2 251.2
Private equity funds | Aerospace/Defense/Government    
Debt and Equity Securities, FV-NI [Line Items]    
Fair Value 139.9 144.0
Unfunded Commitments 38.0 39.9
Private equity funds | Financial services    
Debt and Equity Securities, FV-NI [Line Items]    
Fair Value 105.3 104.2
Unfunded Commitments 50.8 23.7
Private equity funds | Real estate    
Debt and Equity Securities, FV-NI [Line Items]    
Fair Value 3.0 3.0
Unfunded Commitments 2.2 2.2
Hedge funds    
Debt and Equity Securities, FV-NI [Line Items]    
Fair Value 231.3 144.0
Unfunded Commitments 0.0 0.0
Hedge funds | Long/short all cap global    
Debt and Equity Securities, FV-NI [Line Items]    
Fair Value 170.0 110.6
Unfunded Commitments 0.0 0.0
Hedge funds | Long/short equity financials and business services    
Debt and Equity Securities, FV-NI [Line Items]    
Fair Value 61.3 33.4
Unfunded Commitments $ 0.0 $ 0.0