Short-Term Borrowings (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Daily borrowings under credit arrangements	$ 561,200,000		$ 561,200,000
Uncommitted secured lines of credit			680,000,000
Committed revolving credit facility	100,000,000		100,000,000
Interest rate percentage over one-month Eurocurrency rate			1.00%
Short-term borrowings from banks	133,100,000		133,100,000		304,700,000
Company-owned securities collateralized value	648,111,000		648,111,000		607,586,000
Weighted average daily interest rates	1.11%		1.11%		1.14%
Debt instrument interest rate during period	1.33%	1.15%	1.28%	1.15%
Average outstanding securities	246,800,000	151,300,000	290,400,000	201,000,000
Stock loan balance	169,283,000		169,283,000		19,218,000
Stifel Nicolaus [Member]
Short-term borrowings from banks	133,100,000		133,100,000
Debt instrument interest rate during period	0.23%	0.14%	0.16%	0.13%
Average outstanding securities	120,700,000	150,600,000	89,000,000	150,000,000
Company Owned Securities [Member]
Company-owned securities collateralized value	411,800,000		411,800,000		530,700,000
Stock Loan Balance [Member] | Stifel Nicolaus [Member]
Weighted average daily interest rates	0.33%		0.33%		0.24%
Stock loan balance	$ 169,300,000		$ 169,300,000		$ 19,200,000