Short-Term Borrowings (Details) (USD $)	3 Months Ended
	Mar. 31, 2015 item	Mar. 31, 2014
Short-term Debt [Line Items]
Daily borrowings under credit arrangements	$ 80,300,000
Uncommitted secured lines of credit	780,000,000
Committed revolving credit facility	100,000,000
Number of banks	4
Compensating balances	0
Outstanding on our revolving credit facility	0
Short-term borrowings from banks	20,500,000
Weighted average daily interest rates	1.00%
Debt instrument interest rate during period	1.00%	1.13%
Average outstanding securities	13,500,000	97,700,000
Stifel Nicolaus [Member]
Short-term Debt [Line Items]
Short-term borrowings from banks	20,500,000
Debt instrument interest rate during period	0.17%	0.17%
Average outstanding securities	12,100,000	72,500,000
Company Owned Securities [Member]
Short-term Debt [Line Items]
Company-owned securities collateralized value	$ 298,400,000