v2.4.0.6
Securities Available for Sale, Residential Mortgage-Backed Securities, Credit Loss Component (Details) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Credit Impairment Losses On Residential Mortgage Backed Securities [Abstract]      
Securities available for sale $ 256 $ 541 $ 692
Residential [Member]
     
Credit Impairment Losses On Residential Mortgage Backed Securities [Abstract]      
Securities available for sale 84 252 175
Significant inputs (non-agency - non-investment grade MBS) [Abstract]      
Expected remaining life of loan losses From 1.00% 0.00% 1.00%
Expected remaining life of loan losses To 44.00% 48.00% 43.00%
Credit impairment distribution [Abstract]      
0 - 10% range 77.00% 42.00% 52.00%
10 - 20% range 11.00% 18.00% 29.00%
20 - 30% range 4.00% 28.00% 17.00%
Greater than 30% 8.00% 12.00% 2.00%
Weighted average 8.00% 12.00% 9.00%
Current subordination levels [Abstract]      
Current subordination levels From 0.00% 0.00% 0.00%
Current subordination levels To 57.00% 25.00% 25.00%
Current subordination levels Weighted average 2.00% 4.00% 7.00%
Prepayment speed (annual CPR)      
Prepayment speed From 5.00% 3.00% 2.00%
Prepayment speed To 29.00% 19.00% 27.00%
Prepayment speed Weighted average 15.00% 11.00% 14.00%
Investment Grade [Member] | Residential [Member]
     
Credit Impairment Losses On Residential Mortgage Backed Securities [Abstract]      
Securities available for sale 0 5 5
Non-investment Grade [Member] | Residential [Member]
     
Credit Impairment Losses On Residential Mortgage Backed Securities [Abstract]      
Securities available for sale $ 84 $ 247 $ 170