Bank Deposits (Narrative) (Details) - USD ($) $ in Millions	Sep. 30, 2022	Dec. 31, 2021
Bank Deposits [Line Items]
Weighted average interest rate on deposits	0.26%	0.02%
Brokerage Customers Deposits [Member]
Bank Deposits [Line Items]
Deposits of related parties	$ 20,000.0	$ 21,300.0
Stifel Nicolaus [Member]
Bank Deposits [Line Items]
Interest bearing and time deposits of executive officers, directors, and affiliates	$ 5.1	$ 8.6