Securitizations and Variable Interest Entities, Key Economic Assumptions - Mortgage Servicing Rights (Details) (USD $)	9 Months Ended	12 Months Ended
	Sep. 30, 2012 years	Dec. 31, 2011 years
Residential Mortgage Servicing [Member]
Sensitivity Analysis of Fair Value of Interests Continued to be Held by Transferor, Servicing Assets or Liabilities, Impact of Adverse Change in Assumption [Line Items]
Fair value of interests held	$ 10,956,000,000	$ 12,918,000,000
Expected weighted-average life (in years)	4.5	5.1
Prepayment speed assumption (annual CPR)	17.20%	14.80%
Decrease in fair value from 10% adverse change	853,000,000	895,000,000
Decrease in fair value from 25% adverse change	1,994,000,000	2,105,000,000
Discount rate assumption	7.20%	7.10%
Decrease in fair value from 100 basis point increase	513,000,000	566,000,000
Decrease in fair value from 200 basis point increase	981,000,000	1,081,000,000
Cost to service assumption ($ per loan)	219	218
Decrease in fair value from 10% adverse change	589	582
Decrease in fair value from 25% adverse change	1,472	1,457
Interest-Only Strips [Member]
Sensitivity Analysis of Fair Value of Interests Continued to be Held by Transferor, Servicing Assets or Liabilities, Impact of Adverse Change in Assumption [Line Items]
Fair value of interests held	201,000,000	230,000,000
Expected weighted-average life (in years)	4.1	4.6
Prepayment speed assumption (annual CPR)	10.70%	10.70%
Decrease in fair value from 10% adverse change	5,000,000	6,000,000
Decrease in fair value from 25% adverse change	12,000,000	15,000,000
Discount rate assumption	16.60%	15.60%
Decrease in fair value from 100 basis point increase	5,000,000	6,000,000
Decrease in fair value from 200 basis point increase	9,000,000	12,000,000
Subordinated bonds [Member] | Commercial Securitizations [Member]
Sensitivity Analysis of Fair Value of Interests Continued to be Held by Transferor, Servicing Assets or Liabilities, Impact of Adverse Change in Assumption [Line Items]
Fair value of interests held	247,000,000	240,000,000
Expected weighted-average life (in years)	5.0	5.3
Discount rate assumption	4.60%	3.80%
Decrease in fair value from 100 basis point increase	10,000,000	9,000,000
Decrease in fair value from 200 basis point increase	19,000,000	18,000,000
Credit loss assumption	10.90%	10.70%
Decrease in fair value from 10% higher losses	10,000,000	8,000,000
Decrease in fair value from 25% higher losses	18,000,000	18,000,000
Subordinated bonds [Member] | Consumer Securitizations [Member]
Sensitivity Analysis of Fair Value of Interests Continued to be Held by Transferor, Servicing Assets or Liabilities, Impact of Adverse Change in Assumption [Line Items]
Fair value of interests held	44,000,000	45,000,000
Expected weighted-average life (in years)	6.0	6.1
Prepayment speed assumption (annual CPR)	6.80%	6.90%
Decrease in fair value from 10% adverse change	0	0
Decrease in fair value from 25% adverse change	0	1,000,000
Discount rate assumption	8.70%	11.90%
Decrease in fair value from 100 basis point increase	2,000,000	2,000,000
Decrease in fair value from 200 basis point increase	4,000,000	4,000,000
Credit loss assumption	0.40%	0.50%
Decrease in fair value from 10% higher losses	0	0
Decrease in fair value from 25% higher losses	0	0
Senior bonds [Member] | Commercial Securitizations [Member]
Sensitivity Analysis of Fair Value of Interests Continued to be Held by Transferor, Servicing Assets or Liabilities, Impact of Adverse Change in Assumption [Line Items]
Fair value of interests held	870,000,000	852,000,000
Expected weighted-average life (in years)	5.0	4.4
Discount rate assumption	2.40%	2.40%
Decrease in fair value from 100 basis point increase	36,000,000	31,000,000
Decrease in fair value from 200 basis point increase	70,000,000	59,000,000
Credit loss assumption	0.00%	0.00%
Decrease in fair value from 10% higher losses	0	0
Decrease in fair value from 25% higher losses	0	0
Senior bonds [Member] | Consumer Securitizations [Member]
Sensitivity Analysis of Fair Value of Interests Continued to be Held by Transferor, Servicing Assets or Liabilities, Impact of Adverse Change in Assumption [Line Items]
Fair value of interests held	0	321,000,000
Expected weighted-average life (in years)	0	5.6
Prepayment speed assumption (annual CPR)	0.00%	13.90%
Decrease in fair value from 10% adverse change	0	2,000,000
Decrease in fair value from 25% adverse change	0	4,000,000
Discount rate assumption	0.00%	7.10%
Decrease in fair value from 100 basis point increase	0	12,000,000
Decrease in fair value from 200 basis point increase	0	24,000,000
Credit loss assumption	0.00%	4.50%
Decrease in fair value from 10% higher losses	0	1,000,000
Decrease in fair value from 25% higher losses	$ 0	$ 2,000,000