Short-Term Borrowings (Narrative) (Details)	12 Months Ended
	Dec. 31, 2011 USD ($)	Dec. 31, 2011 CAD	Dec. 31, 2010 USD ($)
Short-Term Borrowings [Abstract]
Weighted-average interest rate of short-term borrowings	0.64%		1.10%
Fair value of U.S. government securities	$ 2,980,000,000
Average balances of securities purchased under agreements to resell and securities sold under agreements to repurchase	20,970,000,000		16,270,000,000
Commercial paper authorized	3,000,000,000
Commercial paper maturity period, days	270
Commercial paper, outstanding	2,380,000,000		2,800,000,000
Bank notes authorized	5,000,000,000
Subordinated bank notes authorized	1,000,000,000
Bank note under board authority	2,050,000,000
Bank notes outstanding			2,450,000,000
Line of credit	$ 787,000,000	800,000,000