Investment Securities (Parenthetical) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Investment [Line Items]
Investment securities (Note 3)	$ 43,661	$ 48,439
OTTI previously recognized through OCI on securities held	(145)
Residential Mortgage Backed Securities [Member] | Mortgage-backed Securities, Issued by Private Enterprises [Member]
Investment [Line Items]
Investment securities (Note 3)	770
Residential Mortgage Backed Securities [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Investment [Line Items]
Investment securities (Note 3)	$ 1,346