Fair Value Disclosures (Schedule Of Assets And Liabilities Measured On Recurring Basis At Fair Value) (Details) (USD $)	Mar. 31, 2013		Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives	$ 206,920,000
Total available for sale securities	2,794,516,000		3,356,992,000
Cash and cash equivalents	3,140,421,000		145,960,000
Investments in managed funds	59,976,000
Cash and securities segregated and on deposit for regulatory purposes	3,728,742,000	[1]
Securities received as collateral	25,338,000
Derivatives	220,697,000
Total trading liabilities	9,766,876,000
Obligation to return securities received as collateral	25,338,000
US government and Federal agency securities segregated for regulatory purposes	357,200,000
Trading Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Corporate equity securities	1,934,184,000
Corporate debt securities	1,845,617,000
U.S. government and federal agency securities	2,567,397,000
Sovereign obligations	2,477,844,000
Loans	452,007,000
Derivatives	220,697,000
Physical commodities	167,550,000
Total trading liabilities	9,766,876,000
Trading Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Corporate equity securities	1,688,607,000
Corporate debt securities	3,371,464,000
Collateralized debt obligations	144,921,000
U.S. government and federal agency securities	909,640,000
Municipal securities	603,957,000
Sovereign obligations	3,496,858,000
Loans and other receivables	968,360,000
Derivatives	206,920,000
Investments at fair value	71,103,000
Investment in associated companies carried at fair value			1,077,172,000
Physical commodities	157,299,000
Total trading assets	16,413,535,000
Available For Sale Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Corporate equity securities	460,844,000		934,823,000
Corporate debt securities	28,666,000		16,648,000
U.S. government and federal agency securities	1,474,586,000		1,663,512,000
Other	362,000		884,000
Total available for sale securities	2,794,516,000		3,356,992,000
Residential Mortgage-Backed Securities [Member] | Trading Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage- and asset-backed securities, liabilities	96,074,000
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	3,789,636,000
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	649,082,000		601,456,000
Commercial Mortgage-Backed Securities [Member] | Trading Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage- and asset-backed securities, liabilities	1,811,000
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	933,614,000
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	89,047,000		59,113,000
Other Asset-Backed Securities [Member] | Trading Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage- and asset-backed securities, liabilities	3,695,000
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	71,156,000
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	91,929,000		80,556,000
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	3,140,421,000	[2]	145,960,000	[2]
Cash and securities segregated and on deposit for regulatory purposes	3,728,742,000	[1],[2]
Securities received as collateral	25,338,000	[2]
Obligation to return securities received as collateral	25,338,000	[2]
Level 1 [Member] | Trading Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Corporate equity securities	1,697,826,000	[2]
U.S. government and federal agency securities	2,567,397,000	[2]
Sovereign obligations	1,268,489,000	[2]
Derivatives	435,602,000	[2]
Total trading liabilities	5,969,314,000	[2]
Level 1 [Member] | Trading Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Corporate equity securities	1,443,328,000	[2]
U.S. government and federal agency securities	776,846,000	[2]
Sovereign obligations	2,041,200,000	[2]
Derivatives	445,895,000	[2]
Investment in associated companies carried at fair value			1,077,172,000	[2]
Total trading assets	4,707,269,000	[2]
Level 1 [Member] | Available For Sale Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Corporate equity securities	460,844,000	[2]	934,823,000	[2]
U.S. government and federal agency securities	1,468,588,000	[2]	1,657,022,000	[2]
Total available for sale securities	1,929,432,000	[2]	2,591,845,000	[2]
Level 2 [Member] | Trading Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Corporate equity securities	236,320,000	[2]
Corporate debt securities	1,845,617,000	[2]
Sovereign obligations	1,209,355,000	[2]
Loans	444,609,000	[2]
Derivatives	1,640,905,000	[2]
Physical commodities	167,550,000	[2]
Total trading liabilities	5,644,394,000	[2]
Level 2 [Member] | Trading Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Corporate equity securities	232,045,000	[2]
Corporate debt securities	3,339,644,000	[2]
Collateralized debt obligations	115,145,000	[2]
U.S. government and federal agency securities	132,794,000	[2]
Municipal securities	603,957,000	[2]
Sovereign obligations	1,455,658,000	[2]
Loans and other receivables	797,374,000	[2]
Derivatives	1,491,718,000	[2]
Investments at fair value	1,036,000	[2]
Physical commodities	157,299,000	[2]
Total trading assets	12,932,604,000	[2]
Level 2 [Member] | Available For Sale Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Corporate debt securities	28,666,000	[2]	16,648,000	[2]
U.S. government and federal agency securities	5,998,000	[2]	6,490,000	[2]
Other	362,000	[2]	884,000	[2]
Total available for sale securities	865,084,000	[2]	765,147,000	[2]
Level 2 [Member] | Residential Mortgage-Backed Securities [Member] | Trading Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage- and asset-backed securities, liabilities	94,532,000	[2]
Level 2 [Member] | 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	3,620,210,000	[2]
Level 2 [Member] | 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	649,082,000	[2]	601,456,000	[2]
Level 2 [Member] | Commercial Mortgage-Backed Securities [Member] | Trading Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage- and asset-backed securities, liabilities	1,811,000	[2]
Level 2 [Member] | 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	915,820,000	[2]
Level 2 [Member] | 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	89,047,000	[2]	59,113,000	[2]
Level 2 [Member] | Other Asset-Backed Securities [Member] | Trading Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage- and asset-backed securities, liabilities	3,695,000	[2]
Level 2 [Member] | 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	69,904,000	[2]
Level 2 [Member] | 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	91,929,000	[2]	80,556,000	[2]
Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in managed funds	59,976,000
Level 3 [Member] | Trading Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Corporate equity securities	38,000
Loans	7,398,000
Derivatives	11,405,000
Total trading liabilities	20,383,000
Level 3 [Member] | Trading Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Corporate equity securities	13,234,000
Corporate debt securities	31,820,000
Collateralized debt obligations	29,776,000
Loans and other receivables	170,986,000
Derivatives	220,000
Investments at fair value	70,067,000
Total trading assets	504,575,000
Level 3 [Member] | Residential Mortgage-Backed Securities [Member] | Trading Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Mortgage- and asset-backed securities, liabilities	1,542,000
Level 3 [Member] | 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	169,426,000
Level 3 [Member] | 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	17,794,000
Level 3 [Member] | 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	1,252,000
Counterparty and Cash Collateral Netting [Member] | Trading Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives	(1,867,215,000)	[3]
Total trading liabilities	(1,867,215,000)	[3]
Counterparty and Cash Collateral Netting [Member] | Trading Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivatives	(1,730,913,000)	[3]
Total trading assets	$ (1,730,913,000)	[3]

[1] Includes U.S. government securities segregated for regulatory purposes with a fair value of $357.2 million.

[2] There were no transfers between Level 1 and Level 2 during 2013 or 2012.

[3] Represents counterparty and cash collateral netting across the levels of the fair value hierarchy for positions with the same counterparty.