Fair Value Disclosures (Schedule Of Assets And Liabilities Measured On Recurring Basis At Fair Value) (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments at fair value based on NAV	$ 30,300	$ 36,700
Derivatives	330,977	262,799
Counterparty/cash-collateral netting, Assets	(5,030,887)	(4,165,446)
Total trading assets, excluding Investments at fair value based on NAV	16,555,205	18,256,356
Total available for sale securities	364,144	207,355
Cash and cash equivalents	3,030,936	3,638,648
Cash and securities segregated and on deposit for regulatory purposes or deposited with clearing and depository organizations	836,871	751,084
Derivatives	406,759	218,243
Counterparty/cash-collateral netting, Liabilities	(5,118,214)	(4,257,998)
Total trading liabilities	8,029,906	6,840,430
Other secured financings	46,773	68,345
Debt-structured notes	92,993
Trading Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Corporate equity securities	1,935,802	1,464,604
Corporate debt securities	1,964,988	1,556,941
Collateralized debt obligations		1,488,121
U.S. government and federal agency securities	1,349,746	1,342,996
Sovereign obligations	1,772,047	117
Loans	599,519	769,408
Derivatives	406,759	218,243
Counterparty/cash-collateral netting, Liabilities	(5,118,214)	(4,257,998)
US Treasury Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and securities segregated and on deposit for regulatory purposes or deposited with clearing and depository organizations	99,900
Trading Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Corporate equity securities	3,018,870	2,977,881
Corporate debt securities	2,827,280	2,893,041
Collateralized debt obligations	115,473	174,236
U.S. government and federal agency securities	2,569,421	2,645,651
Municipal securities	638,929	487,141
Sovereign obligations	2,295,884	2,659,441
Loans and other receivables	1,709,718	1,312,333
Derivatives	330,977	262,799
Counterparty/cash-collateral netting, Assets	(5,030,887)	(4,165,446)
Investments at fair value	302,271	226,018
Investment in FXCM	508,400	625,689
Available For Sale Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Corporate equity securities	69,626	73,579
Corporate debt securities	2,530	4,744
U.S. government and federal agency securities	240,696	63,945
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total trading assets, excluding Investments at fair value based on NAV	6,768,819	6,611,880
Total available for sale securities	310,322	137,524
Cash and cash equivalents	3,030,936	3,638,648
Cash and securities segregated and on deposit for regulatory purposes or deposited with clearing and depository organizations	836,871	751,084
Total trading liabilities	3,877,279	3,754,147
Other secured financings	0	0
Debt-structured notes	0
Level 1 [Member] | Trading Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Corporate equity securities	1,846,996	1,428,048
Corporate debt securities	0	0
Collateralized debt obligations		1,488,121
U.S. government and federal agency securities	1,349,746	837,614
Sovereign obligations	678,659	0
Loans	0	0
Derivatives	1,878	364
Level 1 [Member] | Trading Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Corporate equity securities	2,828,939	2,803,243
Corporate debt securities	0	0
Collateralized debt obligations	0	0
U.S. government and federal agency securities	2,476,399	2,555,018
Municipal securities	0	0
Sovereign obligations	1,450,033	1,251,366
Loans and other receivables	0	0
Derivatives	13,448	2,253
Investments at fair value	0	0
Investment in FXCM	0	0
Level 1 [Member] | Available For Sale Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Corporate equity securities	69,626	73,579
Corporate debt securities	0	0
U.S. government and federal agency securities	240,696	63,945
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total trading assets, excluding Investments at fair value based on NAV	13,657,809	14,495,857
Total available for sale securities	53,822	69,831
Cash and cash equivalents	0	0
Cash and securities segregated and on deposit for regulatory purposes or deposited with clearing and depository organizations	0	0
Total trading liabilities	9,248,210	7,314,231
Other secured financings	46,305	67,801
Debt-structured notes	92,993
Level 2 [Member] | Trading Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Corporate equity securities	88,806	36,518
Corporate debt securities	1,964,988	1,556,941
Collateralized debt obligations		0
U.S. government and federal agency securities	0	505,382
Sovereign obligations	1,093,388	117
Loans	597,623	758,939
Derivatives	5,502,360	4,456,334
Level 2 [Member] | Trading Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Corporate equity securities	141,115	133,732
Corporate debt securities	2,803,167	2,867,165
Collateralized debt obligations	62,763	89,144
U.S. government and federal agency securities	93,022	90,633
Municipal securities	638,929	487,141
Sovereign obligations	845,731	1,407,955
Loans and other receivables	1,605,319	1,123,044
Derivatives	5,332,105	4,406,207
Investments at fair value	29,000	26,224
Investment in FXCM	0	0
Level 2 [Member] | Available For Sale Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Corporate equity securities	0	0
Corporate debt securities	2,530	4,744
U.S. government and federal agency securities	0	0
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total trading assets, excluding Investments at fair value based on NAV	1,159,464	1,314,065
Total available for sale securities	0	0
Cash and cash equivalents	0	0
Cash and securities segregated and on deposit for regulatory purposes or deposited with clearing and depository organizations	0	0
Total trading liabilities	22,631	30,050
Other secured financings	468	544
Debt-structured notes	0
Level 3 [Member] | Trading Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Corporate equity securities	0	38
Corporate debt securities	0	0
Collateralized debt obligations		0
U.S. government and federal agency securities	0	0
Sovereign obligations	0	0
Loans	1,896	10,469
Derivatives	20,735	19,543
Level 3 [Member] | Trading Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Corporate equity securities	48,816	40,906
Corporate debt securities	24,113	25,876
Collateralized debt obligations	52,710	85,092
U.S. government and federal agency securities	0	0
Municipal securities	0	0
Sovereign obligations	120	120
Loans and other receivables	104,399	189,289
Derivatives	16,311	19,785
Investments at fair value	273,271	199,794
Investment in FXCM	508,400	625,689
Level 3 [Member] | Available For Sale Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Corporate equity securities	0	0
Corporate debt securities	0	0
U.S. government and federal agency securities	0	0
Residential Mortgage-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total available for sale securities	28,142	23,240
Residential Mortgage-Backed Securities [Member] | Trading Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Residential mortgage-backed securities	1,045
Residential Mortgage-Backed Securities [Member] | Trading Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage- and asset-backed securities, assets	1,417,281	2,801,333
Residential Mortgage-Backed Securities [Member] | Available For Sale Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage- and asset-backed securities, assets	28,142	23,240
Residential Mortgage-Backed Securities [Member] | Level 1 [Member] | Trading Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Residential mortgage-backed securities	0
Residential Mortgage-Backed Securities [Member] | Level 1 [Member] | Trading Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage- and asset-backed securities, assets	0	0
Residential Mortgage-Backed Securities [Member] | Level 1 [Member] | Available For Sale Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage- and asset-backed securities, assets	0	0
Residential Mortgage-Backed Securities [Member] | Level 2 [Member] | Trading Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Residential mortgage-backed securities	1,045
Residential Mortgage-Backed Securities [Member] | Level 2 [Member] | Trading Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage- and asset-backed securities, assets	1,353,973	2,731,070
Residential Mortgage-Backed Securities [Member] | Level 2 [Member] | Available For Sale Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage- and asset-backed securities, assets	28,142	23,240
Residential Mortgage-Backed Securities [Member] | Level 3 [Member] | Trading Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Residential mortgage-backed securities	0
Residential Mortgage-Backed Securities [Member] | Level 3 [Member] | Trading Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage- and asset-backed securities, assets	63,308	70,263
Residential Mortgage-Backed Securities [Member] | Level 3 [Member] | Available For Sale Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage- and asset-backed securities, assets	0	0
Commercial Mortgage-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total available for sale securities	4,091	2,374
Commercial Mortgage-Backed Securities [Member] | Trading Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage- and asset-backed securities, assets	640,272	1,029,239
Commercial Mortgage-Backed Securities [Member] | Available For Sale Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage- and asset-backed securities, assets	4,091	2,374
Commercial Mortgage-Backed Securities [Member] | Level 1 [Member] | Trading Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage- and asset-backed securities, assets	0	0
Commercial Mortgage-Backed Securities [Member] | Level 1 [Member] | Available For Sale Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage- and asset-backed securities, assets	0	0
Commercial Mortgage-Backed Securities [Member] | Level 2 [Member] | Trading Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage- and asset-backed securities, assets	615,289	1,014,913
Commercial Mortgage-Backed Securities [Member] | Level 2 [Member] | Available For Sale Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage- and asset-backed securities, assets	4,091	2,374
Commercial Mortgage-Backed Securities [Member] | Level 3 [Member] | Trading Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage- and asset-backed securities, assets	24,983	14,326
Commercial Mortgage-Backed Securities [Member] | Level 3 [Member] | Available For Sale Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage- and asset-backed securities, assets	0	0
Other Asset-Backed Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total available for sale securities	19,059	39,473
Other Asset-Backed Securities [Member] | Trading Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage- and asset-backed securities, assets	180,429	161,554
Other Asset-Backed Securities [Member] | Available For Sale Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage- and asset-backed securities, assets	19,059	39,473
Other Asset-Backed Securities [Member] | Level 1 [Member] | Trading Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage- and asset-backed securities, assets	0	0
Other Asset-Backed Securities [Member] | Level 1 [Member] | Available For Sale Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage- and asset-backed securities, assets	0	0
Other Asset-Backed Securities [Member] | Level 2 [Member] | Trading Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage- and asset-backed securities, assets	137,396	118,629
Other Asset-Backed Securities [Member] | Level 2 [Member] | Available For Sale Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage- and asset-backed securities, assets	19,059	39,473
Other Asset-Backed Securities [Member] | Level 3 [Member] | Trading Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage- and asset-backed securities, assets	43,033	42,925
Other Asset-Backed Securities [Member] | Level 3 [Member] | Available For Sale Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage- and asset-backed securities, assets	$ 0	$ 0