Investment Securities - Fair Value of Hedge Funds Subject to Restrictions on Redemption Frequency (Details) $ in Millions	Dec. 31, 2022 USD ($) fund	Dec. 31, 2021 USD ($)
Total private equity funds and hedge funds included in other long-term investments
Investment securities
Other long-term investments largest single investment	$ 49.0	$ 31.3
Trading security, fair value	197.8	153.8
Fair value unfunded commitments	$ 94.3	44.0
Private equity funds
Investment securities
Number of investments | fund	16
Trading security, fair value	$ 140.6	141.8
Fair value unfunded commitments	94.3	44.0
Private equity funds | Aerospace/Defense/Government
Investment securities
Trading security, fair value	59.4	69.8
Fair value unfunded commitments	37.5	11.8
Private equity funds | Financial services
Investment securities
Trading security, fair value	77.1	67.7
Fair value unfunded commitments	54.3	29.3
Private equity funds | Real estate
Investment securities
Trading security, fair value	4.1	4.3
Fair value unfunded commitments	$ 2.5	2.9
Hedge funds
Investment securities
Number of investments | fund	2
Trading security, fair value	$ 57.2	12.0
Fair value unfunded commitments	0.0	0.0
Hedge funds | Long/short equity financials and business services
Investment securities
Trading security, fair value	49.0	0.0
Fair value unfunded commitments	0.0	0.0
Hedge funds | European small/mid cap
Investment securities
Trading security, fair value	8.2	12.0
Fair value unfunded commitments	$ 0.0	$ 0.0