FAIR VALUE MEASUREMENT (Details 3) (USD $)	3 Months Ended			9 Months Ended		3 Months Ended		9 Months Ended	3 Months Ended							9 Months Ended	3 Months Ended		9 Months Ended
	Mar. 31, 2011	Sep. 30, 2011 Federal funds sold and securities borrowed or purchased under agreements to resell	Sep. 30, 2011 Loans	Sep. 30, 2011 Loans	Sep. 30, 2012 Long-term debt	Mar. 31, 2011 Mortgage-backed securities	Sep. 30, 2012 U.S. government-sponsored agency guaranteed Investments:	Sep. 30, 2012 U.S. government-sponsored agency guaranteed Investments:	Mar. 31, 2011 Prime	Mar. 31, 2011 Alt-A	Mar. 31, 2011 Subprime	Mar. 31, 2011 Commercial	Mar. 31, 2011 State and municipal securities	Mar. 31, 2011 Corporate	Mar. 31, 2011 Asset-backed securities	Sep. 30, 2012 Other debt securities Trading account assets	Sep. 30, 2012 Non-marketable equity securities Investments:	Mar. 31, 2011 Non-marketable equity securities Investments:	Sep. 30, 2012 Non-marketable equity securities Investments:
Fair Value Asset and Liabilities Measured on Recurring Basis Unobservable Input Changes
Transfers from Level 3 to Level 2					$ 1,100,000,000		$ 1,300,000,000	$ 2,800,000,000
Purchases of securities																		2,800,000,000
Sales of securities																	1,500,000,000		2,800,000,000
Investments held-to-maturity reclassified to Trading account assets	4,300,000,000					2,800,000,000			1,000,000,000	1,500,000,000	200,000,000	100,000,000	900,000,000	300,000,000	200,000,000
Transfers from Level 2 to Level 3		$ 1,100,000,000	$ 600,000,000	$ 400,000,000			$ 500,000,000	$ 500,000,000								$ 1,000,000,000
The threshold tenor of repo curves to classify structured reverse repos as level 3		5 years