Segment Operating Results (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Segment Reporting Information [Line Items]
Net Revenues	$ 427,007	$ 415,327
Operating Expenses	352,446	324,151
Other Expenses	25,258	7,366
Income Before Income from Equity Method Investments and Income Taxes	49,303	83,810
Income from Equity Method Investments	3,128	2,211
Pre-Tax Income	52,431	86,021
Identifiable Segment Assets	2,221,552	1,844,937	$ 2,598,613
Investment Banking [Member]
Segment Reporting Information [Line Items]
Net Revenues	413,656	401,188
Operating Expenses	339,795	311,910
Other Expenses	25,226	7,258
Income Before Income from Equity Method Investments and Income Taxes	48,635	82,020
Income from Equity Method Investments	536	255
Pre-Tax Income	49,171	82,275
Identifiable Segment Assets	2,070,887	1,650,115
Investment Management [Member]
Segment Reporting Information [Line Items]
Net Revenues	13,351	14,139
Operating Expenses	12,651	12,241
Other Expenses	32	108
Income Before Income from Equity Method Investments and Income Taxes	668	1,790
Income from Equity Method Investments	2,592	1,956
Pre-Tax Income	3,260	3,746
Identifiable Segment Assets	$ 150,665	$ 194,822