Fair Value Disclosures (Summary Of Changes In Fair Value Of Financial Assets And Liabilities Classified As Level 3) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2014		Jun. 30, 2013		Jun. 30, 2014		Jun. 30, 2013
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Total gains (losses) (realized and unrealized)	$ 16,600		$ (3,400)		$ 33,700		$ (3,400)
Total gains (losses) (realized and unrealized)	(8,500)		400		(12,100)		400
Corporate Equity Securities [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance	12,341		13,234	[1]	9,884		13,234	[1]
Total gains (losses) (realized and unrealized)	(178)	[2]	2,906	[1],[2]	(1,583)	[2]	2,906	[1],[2]
Purchases	90		5,023	[1]	608		5,023	[1]
Sales	(84)		(2,984)	[1]	(370)		(2,984)	[1]
Net transfers into/ (out of) Level 3	4,233		1,398	[1]	7,863	[2]	1,398	[1]
Ending Balance	16,402		19,577	[1]	16,402		19,577	[1]
Change in unrealized gains/(losses) relating to instruments still held	(178)	[2]	2,058	[1],[2]	(494)	[2]	2,058	[1],[2]
Beginning Balance	1,015		38	[1]	38		38	[1]
Total gains (losses) (realized and unrealized)	(977)	[2]
Ending Balance	38		38	[1]	38		38	[1]
Change in unrealized gains/(losses) relating to instruments still held	558	[2]
Corporate Debt Securities [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance	29,315		31,820	[1]	25,666		31,820	[1]
Total gains (losses) (realized and unrealized)	5,659	[2]	(2,867)	[1],[2]	5,116	[2]	(2,867)	[1],[2]
Purchases	1,937		918	[1]	3,835		918	[1]
Sales	(5,831)		(11,989)	[1]	(3,224)		(11,989)	[1]
Net transfers into/ (out of) Level 3	568		733	[1]	255	[2]	733	[1]
Ending Balance	31,648		18,615	[1]	31,648		18,615	[1]
Change in unrealized gains/(losses) relating to instruments still held	7,999	[2]	(2,242)	[1],[2]	7,420	[2]	(2,242)	[1],[2]
Total gains (losses) (realized and unrealized)	(84)	[2]			(203)	[2]
Purchases	(4,082)				(28,319)
Sales	3,012				31,431
Net transfers into/ (out of) Level 3	3,934				(129)	[2]
Ending Balance	2,780				2,780
Change in unrealized gains/(losses) relating to instruments still held	84	[2]			203	[2]
Collateralized Debt Obligations [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance	66,028		29,776	[1]	37,216		29,776	[1]
Total gains (losses) (realized and unrealized)	4,706	[2]	6,698	[1],[2]	14,169	[2]	6,698	[1],[2]
Purchases	19,146		17,864	[1]	36,200		17,864	[1]
Sales	(49,636)		(6,270)	[1]	(55,963)		(6,270)	[1]
Settlements	(331)
Net transfers into/ (out of) Level 3	2,400		(2,944)	[1]	10,691	[2]	(2,944)	[1]
Ending Balance	42,313		45,124	[1]	42,313		45,124	[1]
Change in unrealized gains/(losses) relating to instruments still held	238	[2]	6,148	[1],[2]	5,656	[2]	6,148	[1],[2]
Residential Mortgage-Backed Securities [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance	116,992		169,426	[1]	105,492		169,426	[1]
Total gains (losses) (realized and unrealized)	(791)	[2]	(86)	[1],[2]	(4,114)	[2]	(86)	[1],[2]
Purchases	10,955		57,750	[1]	21,893		57,750	[1]
Sales	(24,618)		(71,534)	[1]	(37,356)		(71,534)	[1]
Settlements	(459)		(5,436)	[1]	(529)		(5,436)	[1]
Net transfers into/ (out of) Level 3	(30,117)		(6,354)	[1]	(13,424)	[2]	(6,354)	[1]
Ending Balance	71,962		143,766	[1]	71,962		143,766	[1]
Change in unrealized gains/(losses) relating to instruments still held	(422)	[2]	(367)	[1],[2]	(1,324)	[2]	(367)	[1],[2]
Beginning Balance			1,542	[1]			1,542	[1]
Purchases			(1,542)	[1]			(1,542)	[1]
Commercial Mortgage-Backed Securities [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance	17,486		17,794	[1]	17,568		17,794	[1]
Total gains (losses) (realized and unrealized)	(903)	[2]	(2,905)	[1],[2]	(2,191)	[2]	(2,905)	[1],[2]
Purchases	18,026		1,403	[1]	32,449		1,403	[1]
Sales	(21,038)		(2,744)	[1]	(29,864)		(2,744)	[1]
Settlements	(1,189)		(1,578)	[1]	(1,710)		(1,578)	[1]
Net transfers into/ (out of) Level 3	11,864		4,098	[1]	7,994	[2]	4,098	[1]
Ending Balance	24,246		16,068	[1]	24,246		16,068	[1]
Change in unrealized gains/(losses) relating to instruments still held	(1,933)	[2]	(3,835)	[1],[2]	(3,236)	[2]	(3,835)	[1],[2]
Other Asset-Backed Securities [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance	2,375		1,252	[1]	12,611		1,252	[1]
Total gains (losses) (realized and unrealized)	(314)	[2]	(4)	[1],[2]	(537)	[2]	(4)	[1],[2]
Purchases	15,686				17,361
Sales					(5,496)
Settlements	(438)				(438)
Net transfers into/ (out of) Level 3	28,135		196	[1]	21,943	[2]	196	[1]
Ending Balance	45,444		1,444	[1]	45,444		1,444	[1]
Change in unrealized gains/(losses) relating to instruments still held	(314)	[2]	(4)	[1],[2]	(569)	[2]	(4)	[1],[2]
Loans And Other Receivables [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance	128,832		170,986	[1]	145,890		170,986	[1]
Total gains (losses) (realized and unrealized)	11,933	[2]	(5,049)	[1],[2]	3,946	[2]	(5,049)	[1],[2]
Purchases	42,278		160,409	[1]	92,579		160,409	[1]
Sales	(48,064)		(24,741)	[1]	(88,674)		(24,741)	[1]
Settlements	(21,482)		(188,268)	[1]	(26,685)		(188,268)	[1]
Net transfers into/ (out of) Level 3	25,146		4,159	[1]	11,587	[2]	4,159	[1]
Ending Balance	138,643		117,496	[1]	138,643		117,496	[1]
Change in unrealized gains/(losses) relating to instruments still held	11,922	[2]	(6,925)	[1],[2]	3,382	[2]	(6,925)	[1],[2]
Investments At Fair Value [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance	138,843		70,067	[1]	101,242		70,067	[1]
Total gains (losses) (realized and unrealized)	4,678	[2]	(1,197)	[1],[2]	30,176	[2]	(1,197)	[1],[2]
Purchases	7,660		5,000	[1]	30,160		5,000	[1]
Sales	(4,101)				(13,722)
Settlements			(2,493)	[1]			(2,493)	[1]
Net transfers into/ (out of) Level 3	(6,628)		4,987	[1]	(7,404)	[2]	4,987	[1]
Ending Balance	140,452		76,364	[1]	140,452		76,364	[1]
Change in unrealized gains/(losses) relating to instruments still held	2,030	[2]	(1,349)	[1],[2]	27,529	[2]	(1,349)	[1],[2]
Investments In Managed Funds [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance	59,528		59,976	[1]	57,285		59,976	[1]
Total gains (losses) (realized and unrealized)	(8,151)	[2]	(927)	[1],[2]	(11,284)	[2]	(927)	[1],[2]
Purchases	11,305		2,532	[1]	13,407		2,532	[1]
Settlements			(6,562)	[1]			(6,562)	[1]
Net transfers into/ (out of) Level 3	(6,563)		122	[1]	(3,289)	[2]	122	[1]
Ending Balance	56,119		55,141	[1]	56,119		55,141	[1]
Change in unrealized gains/(losses) relating to instruments still held	(8,151)	[2]	(926)	[1],[2]	(11,284)	[2]	(926)	[1],[2]
Net Derivatives [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance	5,773	[3]	11,185	[1],[3]	6,905	[3]	11,185	[1],[3]
Total gains (losses) (realized and unrealized)	9,485	[2],[3]	(386)	[1],[2],[3]	11,591	[2],[3]	(386)	[1],[2],[3]
Purchases	(2,150)	[3]			(179)	[3]
Sales	2,149	[3]			(21)	[3]
Settlements	25	[3]			318	[3]
Net transfers into/ (out of) Level 3					(3,332)	[2],[3]
Ending Balance	15,282	[3]	10,799	[1],[3]	15,282	[3]	10,799	[1],[3]
Change in unrealized gains/(losses) relating to instruments still held	(9,485)	[2],[3]	386	[1],[2],[3]	(11,591)	[2],[3]	386	[1],[2],[3]
Loans [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance	10,260		7,398	[1]	22,462		7,398	[1]
Total gains (losses) (realized and unrealized)	62	[2]			754	[2]
Purchases	(9,629)		(7,398)	[1]	(22,491)		(7,398)	[1]
Sales	18,995		15,212	[1]	27,908		15,212	[1]
Settlements	139				139
Net transfers into/ (out of) Level 3	11,707				2,762	[2]
Ending Balance	31,534		15,212	[1]	31,534		15,212	[1]
Change in unrealized gains/(losses) relating to instruments still held	(57)	[2]			(57)	[2]
Other Secured Financings [Member]
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance	30,394				8,711
Purchases	(992)
Settlements	(9,114)				(9,114)
Issuances					20,691
Net transfers into/ (out of) Level 3			2,294	[1]			2,294	[1]
Ending Balance	$ 20,288		$ 2,294	[1]	$ 20,288		$ 2,294	[1]

[1] There were no issuances.

[2] Realized and unrealized gains (losses) are reported in Principal transactions in the Consolidated Statements of Operations.

[3] Net derivatives represent Trading assets - Derivatives and Trading liabilities - Derivatives.