Fair Value Disclosures (Schedule Of Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Thousands	Dec. 31, 2019		Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments-trading	$ 307,852		$ 301,235
Other investments, measured using hierarchy	11,973		9,718
Other investments, Carrying Value	14,864		13,768
Trading securities sold, not yet purchased	77,947		120,122
Quoted Prices In Active Markets (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments-trading	11,105		4,099
Other investments, measured using hierarchy	2,009		5,762
Trading securities sold, not yet purchased	16,827		70,010
Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments-trading	296,747		297,136
Other investments, measured using hierarchy	7,442		1,200
Trading securities sold, not yet purchased	61,120		50,112
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, measured using hierarchy	2,522		2,756
Investments Measured At NAV [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, at fair value	2,891	[1]	4,050	[2]
U.S. government agency MBS and CMOs [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments-trading	196,146		149,651
Trading securities sold, not yet purchased			16
U.S. government agency MBS and CMOs [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments-trading	196,146		149,651
U.S. government agency debt securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments-trading	14,680		14,915
U.S. government agency debt securities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments-trading	14,680		14,915
U.S. government agency MBS [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities sold, not yet purchased			16
U.S. government agency MBS [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities sold, not yet purchased			16
RMBS [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments-trading	15		21
RMBS [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments-trading	15		21
U.S. Treasury securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments-trading	11,105		4,099
Trading securities sold, not yet purchased	16,827		70,010
U.S. Treasury securities [Member] | Quoted Prices In Active Markets (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments-trading	11,105		4,099
Trading securities sold, not yet purchased	16,827		70,010
ABS [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments-trading	100		100
ABS [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments-trading	100		100
SBA loans [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments-trading	27,634		31,496
SBA loans [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments-trading	27,634		31,496
Corporate bonds and redeemable preferred stock [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments-trading	38,503		44,507
Trading securities sold, not yet purchased	58,083		43,957
Corporate bonds and redeemable preferred stock [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments-trading	38,503		44,507
Trading securities sold, not yet purchased	58,083		43,957
Foreign government bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments-trading	844		117
Foreign government bonds [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments-trading	844		117
Municipal bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments-trading	13,737		47,433
Trading securities sold, not yet purchased	20		20
Municipal bonds [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments-trading	13,737		47,433
Trading securities sold, not yet purchased	20		20
Certificates of deposit [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments-trading	841		302
Certificates of deposit [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments-trading	841		302
Derivatives [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments-trading	3,686		8,212
Trading securities sold, not yet purchased	3,017		6,119
Derivatives [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments-trading	3,686		8,212
Trading securities sold, not yet purchased	3,017		6,119
Equity securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments-trading	561		382
Other investments, measured using hierarchy	9,352		6,650
Equity securities [Member] | Quoted Prices In Active Markets (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, measured using hierarchy	2,009		5,775
Equity securities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total investments-trading	561		382
Other investments, measured using hierarchy	7,343		875
Interests in securitizations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, measured using hierarchy	2,522		2,730
Interests in securitizations [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, measured using hierarchy	2,522		2,730
CDOs [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, measured using hierarchy			26
CDOs [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, measured using hierarchy			26
Residential Loans [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, measured using hierarchy	99		325
Residential Loans [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, measured using hierarchy	$ 99		325
Foreign currency forward contracts [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, measured using hierarchy			(13)
Foreign currency forward contracts [Member] | Quoted Prices In Active Markets (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments, measured using hierarchy			$ (13)

[1] As a practical expedient, the Company uses NAV (or its equivalent) to measure the fair value of its investments in the U.S. Insurance JV and the SPAC Funds. The U.S. Insurance JV invests in debt issued by small and medium sized U.S. and Bermuda insurance and reinsurance companies. The SPAC Funds invest in equity securities of SPACs. According to ASC 820, these investments are not categorized within the valuation hierarchy.

[2] As a practical expedient, the Company utilized NAV (or its equivalent) to measure the fair value of its investments in EuroDekania, the U.S. Insurance JV, and the SPAC Funds. EuroDekania sold its remaining investments in 2019. Prior to the sale of its remaining investments, EuroDekania invested in hybrid capital securities of European companies. The U.S. Insurance JV invests in debt issued by small and medium sized U.S. and Bermuda insurance and reinsurance companies. The SPAC Funds invest in equity securities of SPACs. According to ASC 820, these investments are not categorized within the valuation hierarchy.