Short-term Borrowings and Long-term Debt - Narrative (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
Sep. 30, 2022	Dec. 31, 2021
Securities Sold under Agreements to Repurchase
Debt Instrument [Line Items]
Financial instruments, owned, at fair value	$ 5.0	$ 50.5
PPPLF
Debt Instrument [Line Items]
Outstanding borrowings	91.7	271.9
Payables to Securitization Holders \| Consolidated VIEs
Debt Instrument [Line Items]
Restricted cash	6.2	11.2
Payables to Securitization Holders \| Consolidated VIEs \| Loans Held for Investment \| Loans Related to Consolidation of Securitization Trust \| Structured Program Borrowings
Debt Instrument [Line Items]
Financial instruments, owned, at fair value	6.4
Payables to Securitization Holders \| Consolidated VIEs \| Loans Held for Investment and Loans Held for Sale \| Loans Related to Consolidation of Securitization Trust \| Structured Program Borrowings
Debt Instrument [Line Items]
Financial instruments, owned, at fair value		62.7
Subordinated Notes
Debt Instrument [Line Items]
Outstanding borrowings	$ 15.3	$ 15.3
London Interbank Offered Rate (LIBOR) \| Securities Sold under Agreements to Repurchase \| Minimum
Debt Instrument [Line Items]
Borrowings interest rate spread (percent)	4.04%	3.12%
London Interbank Offered Rate (LIBOR) \| Securities Sold under Agreements to Repurchase \| Maximum
Debt Instrument [Line Items]
Borrowings interest rate spread (percent)	6.70%	6.72%
London Interbank Offered Rate (LIBOR) \| Subordinated Notes
Debt Instrument [Line Items]
Borrowings interest rate spread (percent)	4.64%
Credit Facilities and Securities Sold under Repurchase Agreements
Debt Instrument [Line Items]
Aggregate debt outstanding under repurchase transactions	$ 4.8	$ 27.8
Payable to Securitization Note and Certificate Holders at Fair Value \| Consolidated VIEs \| Loans Related to Consolidation of Securitization Trust
Debt Instrument [Line Items]
Payable to Structured Program note and certificate holders	$ 11.2	$ 65.5

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The aggregate fair value as of the balance sheet date of financial instruments and other positions owned by the entity including: (1) mortgages, mortgage-backed and asset backed securities; (2) US government and agency obligations; (3) state and municipal government obligations; (4) other sovereign government debt; (5) corporate obligations; (6) corporate equities; (7) principal investments; (8) derivative contracts; and (9) physical commodities. Includes both pledged and unpledged holdings.

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Amount, excluding unamortized premium (discount) and debt issuance cost, of long-term debt. Excludes lease obligation.

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