Short-Term Borrowings (Details) (USD $)	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Daily borrowings under credit arrangements	$ 486,700,000
Uncommitted secured lines of credit	680,000,000
Committed revolving credit facility	100,000,000
Interest rate percentage over one-month Eurocurrency rate	1.00%
Outstanding on our revolving credit facility	10,000,000
Short-term borrowings from banks	569,800,000		304,700,000
Weighted average daily interest rates	1.18%		1.14%
Debt instrument interest rate during period	1.17%	1.13%
Average outstanding securities	209,400,000	185,300,000
Stock loan balance	65,955,000		19,218,000
Stifel Nicolaus [Member]
Weighted average daily interest rates	0.14%		0.24%
Debt instrument interest rate during period	0.10%	0.13%
Average outstanding securities	64,600,000	156,000,000
Stock loan balance	66,000,000		19,200,000
Company Owned Securities [Member]
Company-owned securities collateralized value	$ 623,100,000		$ 530,700,000