Segment And Geographic Information (Reconciliation Of Assets From Segment To Consolidated) (Details) - USD ($) $ in Thousands		Mar. 31, 2020	Dec. 31, 2019
Segment Reporting, Asset Reconciling Item [Line Items]
Total Assets		$ 6,596,540	$ 8,001,624
Goodwill	[1]	109	7,992
Intangible assets	[1]	166	166
Equity Method Affiliates [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total Assets		5,789	3,799
Operating Segments [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total Assets		6,581,462	7,988,796
Goodwill	[1]	109	7,992
Intangible assets	[1]	166	166
Operating Segments [Member] | Equity Method Affiliates [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total Assets		5,789	3,799
Operating Segments [Member] | Capital Markets [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total Assets		6,564,241	7,968,491
Goodwill	[1]	54	7,937
Intangible assets	[1]	166	166
Operating Segments [Member] | Asset Management [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total Assets		1,348	1,616
Goodwill	[1]	55	55
Operating Segments [Member] | Principal Investing [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total Assets		15,873	18,689
Operating Segments [Member] | Principal Investing [Member] | Equity Method Affiliates [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total Assets		5,789	3,799
Unallocated [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total Assets	[2]	$ 15,078	$ 12,828

[1] Goodwill and intangible assets are allocated to the Capital Markets and Asset Management business segments as indicated in the table above.

[2] Unallocated assets primarily include: (1) amounts due from related parties; (2) furniture and equipment, net; and (3) other assets that are not considered necessary for an understanding of business segment assets. Such amounts are excluded in business segment reporting to the chief operating decision maker.