Short-Term Borrowings (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010	Dec. 31, 2010
Daily borrowings under credit arrangements	$ 340,400,000		$ 340,400,000
Compensating balance requirements			NO
Short-term borrowings from banks	230,400,000		230,400,000		109,600,000
Company-owned securities collateralized value	300,249,000		300,249,000		272,172,000
Weighted average daily interest rates	1.08%		1.08%		1.05%
Debt Instrument, Interest Rate During Period	0.95%	1.03%	1.10%	1.02%
Average outstanding securities	206,000,000	126,800,000	187,700,000	116,600,000
Stock loan balance	114,965,000		114,965,000		27,907,000
Company Owned Securities [Member]
Company-owned securities collateralized value	287,800,000		287,800,000		162,600,000
Stifel Nicolaus [Member]
Weighted average daily interest rates	0.33%		0.33%		0.26%
Debt Instrument, Interest Rate During Period	1.36%	1.53%	1.35%	1.66%
Average outstanding securities	121,800,000	62,600,000	110,200,000	49,500,000
Stock loan balance	$ 115,000,000		$ 115,000,000		$ 27,900,000