Investment Securities - Private Equity Funds and Hedge Funds (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Total private equity funds and hedge funds included in other long-term investments
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value	$ 321.2	$ 312.9
Unfunded Commitments	83.8	57.7
Private equity funds
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value	264.0	248.6
Unfunded Commitments	83.8	57.7
Private equity funds | Aerospace/Defense/Government
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value	173.5	157.2
Unfunded Commitments	46.3	17.4
Private equity funds | Financial services
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value	86.8	87.5
Unfunded Commitments	35.1	37.8
Private equity funds | Real estate
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value	3.7	3.9
Unfunded Commitments	2.4	2.5
Hedge funds
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value	57.2	64.3
Unfunded Commitments	0.0	0.0
Hedge funds | Long/short equity financials and business services
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value	57.2	54.4
Unfunded Commitments	0.0	0.0
Hedge funds | European small/mid cap
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value	0.0	9.9
Unfunded Commitments	$ 0.0	$ 0.0