Investment Securities - Hedge Funds and Private Equity Funds (Details) $ in Millions	9 Months Ended		12 Months Ended
	Sep. 30, 2022 USD ($) fund	Sep. 30, 2021 USD ($)	Dec. 31, 2021 USD ($)
Debt and Equity Securities, FV-NI [Line Items]
Investments in trading securities	$ 97.9	$ 141.6
TIG Advisors, TK Partners, Third Eye Capital Management, Douglass Winthrop Advisors, Granahan Investment Management and Radcliffe Capital Management | Kudu
Debt and Equity Securities, FV-NI [Line Items]
Investments in trading securities			$ 223.4
Private equity funds
Debt and Equity Securities, FV-NI [Line Items]
Number of investments | fund	16
Hedge funds
Debt and Equity Securities, FV-NI [Line Items]
Number of investments | fund	2
Total private equity funds and hedge funds included in other long-term investments
Debt and Equity Securities, FV-NI [Line Items]
Largest single fund investment	$ 49.3		$ 31.3