Segment Operating Results (Information Provides A Reasonable Representation Of Each Segment's Contribution) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Segment Reporting Information [Line Items]
Net Revenues	$ 112,781	$ 163,181	$ 141,204	$ 107,098	$ 101,452	$ 123,025	$ 64,319	$ 87,109	$ 524,264	[1]	$ 375,905	[1]	$ 312,417	[1]
Operating Expenses									427,155		316,016		256,632
Other Expenses									61,297	[2]	23,029	[2]	32,337	[2]
Income Before Income (Loss) from Equity Method Investments and Income Taxes	(1,009)	13,442	11,615	11,764	9,658	18,440	(2,628)	11,390	35,812		36,860		23,448
Income from Equity Method Investments	255	195	69	400	(116)	(131)	(130)	(180)	919		(557)		(1,406)
Income Before Income Taxes	(754)	13,637	11,684	12,164	9,542	18,309	(2,758)	11,210	36,731		36,303		22,042
Identifiable Segment Assets	1,043,592				898,085				1,043,592		898,085		891,160
Investment Banking [Member]
Segment Reporting Information [Line Items]
Net Revenues									428,124	[1]	301,847	[1]	292,634	[1]
Operating Expenses									337,886		240,312		204,399
Other Expenses									55,591	[2]	19,408	[2]	17,728	[2]
Income Before Income (Loss) from Equity Method Investments and Income Taxes									34,647		42,127		70,507
Income from Equity Method Investments									1,101		16
Income Before Income Taxes									35,748		42,143		70,507
Identifiable Segment Assets	530,008				370,329				530,008		370,329		377,303
Investment Management [Member]
Segment Reporting Information [Line Items]
Net Revenues									96,140	[1]	74,058	[1]	19,783	[1]
Operating Expenses									89,269		75,704		52,233
Other Expenses									5,706	[2]	3,621	[2]	14,609	[2]
Income Before Income (Loss) from Equity Method Investments and Income Taxes									1,165		(5,267)		(47,059)
Income from Equity Method Investments									(182)		(573)		(1,406)
Income Before Income Taxes									983		(5,840)		(48,465)
Identifiable Segment Assets	$ 513,584				$ 527,756				$ 513,584		$ 527,756		$ 513,857

[1] Net revenues include Other Revenue, net, allocated to the segments as follows:

[2] Other Expenses are as follows: