FAIR VALUE MEASUREMENT (Details 3) (USD $)	3 Months Ended	12 Months Ended	3 Months Ended			12 Months Ended		12 Months Ended	3 Months Ended				12 Months Ended			3 Months Ended							12 Months Ended	3 Months Ended
	Mar. 31, 2012 Y	Dec. 31, 2011 Interest rate contracts	Mar. 31, 2011 Federal funds sold and securities borrowed or purchased under agreements to resell	Mar. 31, 2012 Trading account assets	Mar. 31, 2011 Trading account assets	Dec. 31, 2011 Trading account assets	Dec. 31, 2009 Trading account assets	Dec. 31, 2010 Derivatives	Mar. 31, 2012 Derivatives Credit derivatives	Mar. 31, 2011 Derivatives Credit derivatives	Mar. 31, 2012 Investments:	Mar. 31, 2011 Investments:	Dec. 31, 2011 Loans	Dec. 31, 2010 Mortgage servicing rights	Dec. 31, 2010 Long-term debt	Mar. 31, 2011 U.S. government-sponsored agency guaranteed Trading account assets	Mar. 31, 2011 Prime Trading account assets	Mar. 31, 2011 Alt-A Trading account assets	Mar. 31, 2011 State and municipal securities Trading account assets	Mar. 31, 2012 Foreign government Trading account assets	Mar. 31, 2012 Corporate Trading account assets	Mar. 31, 2011 Corporate Trading account assets	Dec. 31, 2011 Corporate Trading account assets	Mar. 31, 2012 Equity securities Trading account assets	Mar. 31, 2012 Asset-backed securities Trading account assets	Mar. 31, 2011 Asset-backed securities Trading account assets	Mar. 31, 2012 Other debt securities Trading account assets	Mar. 31, 2011 Non-marketable equity securities Investments:	Mar. 31, 2011 Reclassification of debt securities from held-to-maturity to trading account assets Trading account assets	Mar. 31, 2011 Auction rate securities Trading account assets	Mar. 31, 2012 Securities sold, not yet purchased Trading account assets
Fair Value Asset and Liabilities Measured on Recurring Basis Unobservable Input Changes
Minimum mature period for structured reverse repos to be classified as Level 3 (in years)	5
Increase (decrease) in Level 3 asset balance during period		$ 1,500,000,000	$ 1,600,000,000	$ 1,000,000,000	$ 3,000,000,000				$ (1,500,000,000)	$ 2,200,000,000		$ 2,100,000,000	$ 1,500,000,000			$ 2,800,000,000	$ 1,000,000,000	$ 1,500,000,000	$ 900,000,000			$ 300,000,000				$ 300,000,000		$ 2,500,000,000	$ 4,300,000,000
Net transfers from Level 3 to Level 2			1,500,000,000			2,300,000,000																	1,500,000,000
Purchases of securities																					1,500,000,000	1,800,000,000			2,700,000,000	1,300,000,000	900,000,000	3,200,000,000
Net realized/unrealized gains (losses) included in principal transactions, assets									(1,200,000,000)
Loss recorded on total return swaps referencing returns on corporate loans									600,000,000
Losses on bespoke CDO and index CDO positions due to credit spreads widening									300,000,000
Gains on index positions classified as Level 2									200,000,000
Net settlements								1,900,000,000		1,400,000,000	800,000,000
Net trading losses on derivatives								1,500,000,000
Net terminations of structured notes															1,300,000,000
Transfers from Level 1 to Level 2																								5,000,000							1,000,000
Transfers from Level 2 to Level 1																				111,000,000				358,000,000							66,000,000
Sales of securities												800,000,000									600,000,000	1,500,000,000			3,100,000,000	2,400,000,000	500,000,000			1,100,000,000
Increase (decrease) in level 3 of mortgage servicing rights due to reduction in interest rates														(1,100,000,000)
Investment in certificates issued by trusts of the newly consolidated VIE's that were classified as Level 3							$ 11,100,000,000