Variable Interest Entities (Details) (USD $)	9 Months Ended	12 Months Ended
	Sep. 30, 2011 securities employees years	Dec. 31, 2010 employees years
Variable Interest Entities
Investment securities related to state and political subdivisions	$ 2,850,000,000	$ 2,850,000,000
Variable interest entity, other short-term borrowings	2,380,000,000	2,500,000,000
Weighted-average life of trusts, years	7.4	7.7
Total standby bond-purchase agreement committed to trusts	2,420,000,000
Number of standby purchase agreements utilized	0
Asset-backed securities, fair value	294,000,000	5,010,000,000
Receivable loans purchased	1,080,000,000	2,200,000,000
Commercial paper	0	1,920,000,000
Aggregate notional value of CDOs	1,000,000,000	1,000,000,000
Carrying value of the underlying collateral	$ 275,000,000	$ 323,000,000