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Trading Assets
 12 Months Ended
Dec. 31, 2011
Trading Securities [Abstract]  
Trading Assets
6.    Trading Assets
The fair value for our portfolio of trading assets was as follows.
December 31, ($ in millions)
2011
 
2010
U.S. Treasury
$
—

 
$
77

Mortgage-backed residential
608

 
69

Asset-backed
—

 
94

Total trading securities
608

 
240

Trading derivatives
14

 
—

Total trading assets
$
622

 
$
240

Net unrealized gains on securities held at December 31, (a)
$
19

 
$
21

(a)
Net unrealized gains totaled $203 million at December 31, 2009.