Commitments, Guarantees, And Contingencies (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Customer-owned securities pledged	$ 142.1	$ 80.2
Minimum margin deposit requirements	24.1
Auction rate securities, at par, held by retail clients after issuer redemptions and Stifel repurchases	32.7
Options Clearing Corporation [Member]
Customer-owned securities pledged	88.2
National Securities Clearing Corporation [Member]
Minimum margin deposit requirements	18.4
Minimum [Member]
Minimum margin deposit requirements	$ 56.0