Bank Deposits (Narrative) (Details) - USD ($) $ in Millions	Jun. 30, 2022	Dec. 31, 2021
Bank Deposits [Line Items]
Weighted average interest rate on deposits	0.04%	0.02%
Brokerage Customers Deposits [Member]
Bank Deposits [Line Items]
Deposits of related parties	$ 23,800.0	$ 21,300.0
Stifel Nicolaus [Member]
Bank Deposits [Line Items]
Interest bearing and time deposits of executive officers, directors, and affiliates	$ 1.2	$ 8.6