Bank Deposits (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Bank Deposits [Line Items]
Weighted average interest rate on deposits	0.02%	0.09%
Proceeds from deposits	$ 215.1
Gain (loss) on sale of deposits	4.8
Brokerage Customers Deposits [Member]
Bank Deposits [Line Items]
Deposits of related parties	21,300.0	$ 16,000.0
Stifel Nicolaus [Member]
Bank Deposits [Line Items]
Interest bearing and time deposits of executive officers, directors, and affiliates	$ 8.6	$ 6.7