Investment Securities - Private Equity Funds and Hedge Funds (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
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	$ 299.3	$ 197.8
Unfunded Commitments	69.8	94.3
Private equity funds
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value	239.2	140.6
Unfunded Commitments	69.8	94.3
Private equity funds | Aerospace/Defense/Government
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value	146.4	59.4
Unfunded Commitments	25.5	37.5
Private equity funds | Financial services
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value	88.6	77.1
Unfunded Commitments	41.8	54.3
Private equity funds | Real estate
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value	4.2	4.1
Unfunded Commitments	2.5	2.5
Hedge funds
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Fair Value	60.1	57.2
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	51.1	49.0
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	9.0	8.2
Unfunded Commitments	$ 0.0	$ 0.0