Key Economic Assumptions - Mortgage Servicing Rights (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2011
Mortgage servicing rights [Member]
Key Economic Assumptions and the Sensitivity of the Current Fair Value to Immediate Adverse Changes in those Assumptions, at the Balance Sheet Date [Line Items]
Fair value of interests held	$ 16,583
Expected weighted-average life (in years)	5.7
Prepayment speed assumption (annual CPR)	11.70%
10% adverse change	942
25% adverse change	2,228
Discount rate assumption	7.70%
100 basis point increase	838
200 basis point increase	1,602
Interest-Only Strips [Member]
Key Economic Assumptions and the Sensitivity of the Current Fair Value to Immediate Adverse Changes in those Assumptions, at the Balance Sheet Date [Line Items]
Fair value of interests held	248
Expected weighted-average life (in years)	4.8
Prepayment speed assumption (annual CPR)	10.10%
10% adverse change	6
25% adverse change	16
Discount rate assumption	15.60%
100 basis point increase	7
200 basis point increase	12
Senior bonds [Member]
Key Economic Assumptions and the Sensitivity of the Current Fair Value to Immediate Adverse Changes in those Assumptions, at the Balance Sheet Date [Line Items]
Fair value of interests held	393
Expected weighted-average life (in years)	6.1
Prepayment speed assumption (annual CPR)	11.90%
10% adverse change	1
25% adverse change	3
Discount rate assumption	6.50%
100 basis point increase	16
200 basis point increase	31
Credit loss assumption	4.50%
10% higher losses	1
25% higher losses	2
Subordinated bonds [Member]
Key Economic Assumptions and the Sensitivity of the Current Fair Value to Immediate Adverse Changes in those Assumptions, at the Balance Sheet Date [Line Items]
Fair value of interests held	48
Expected weighted-average life (in years)	5.7
Prepayment speed assumption (annual CPR)	7.90%
10% adverse change	0
25% adverse change	1
Discount rate assumption	11.00%
100 basis point increase	2
200 basis point increase	5
Credit loss assumption	1.20%
10% higher losses	0
25% higher losses	$ 0