Commitments, Guarantees, And Contingencies (Narrative) (Details) - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
Loss Contingencies [Line Items]
Customer-owned securities pledged	$ 342.4	$ 39.2
Minimum margin deposit requirements	59.0
Auction rate securities, at par, held by retail clients after issuer redemptions and Stifel repurchases	8.6
Outstanding committed capital to certain entities	27.7
Business Development Corporations [Member]
Loss Contingencies [Line Items]
Outstanding committed capital to certain entities	16.3
Options Clearing Corporation [Member]
Loss Contingencies [Line Items]
Customer-owned securities pledged	$ 65.5