Investment Securities (Parenthetical) (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2013	Dec. 31, 2012
Investment [Line Items]
Investment securities (Note 3)	$ 43,805	$ 48,439
OTTI previously recognized through OCI on securities held, gross unrealized losses	131
Residential Mortgage Backed Securities [Member] | Mortgage-backed Securities, Issued by Private Enterprises [Member]
Investment [Line Items]
Investment securities (Note 3)	745
Residential Mortgage Backed Securities [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment [Line Items]
Investment securities (Note 3)	$ 1,286