Securitizations and Variable Interest Entities, Retained Interests from Unconsolidated VIEs (Details) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2019 USD ($) $ / loan	Dec. 31, 2018 USD ($) $ / loan
Commercial 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	$ 1,800	$ 2,300
Securitizations and Variable Interest Entities Textual [Abstract]
Percentage of adverse change in interest rate	25.00%	25.00%
Decrease in fair value from 25% adverse change in interest rate	$ 200	$ 320
Residential mortgage servicing rights [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	$ 11,072	$ 14,649
Expected weighted-average life (in years)	5 years 2 months 12 days	6 years 6 months
Key economic assumptions:
Prepayment speed assumption	12.40%	9.90%
Decrease in fair value from:
10% adverse change	$ 521	$ 530
25% adverse change	$ 1,222	$ 1,301
Discount rate assumption	6.90%	8.10%
Decrease in fair value from:
100 basis point increase	$ 437	$ 615
200 basis point increase	$ 838	$ 1,176
Cost to service assumption ($ per loan) | $ / loan	102	106
Decrease in fair value from:
10% adverse change	$ 269	$ 316
25% adverse change	672	787
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	$ 7	$ 16
Expected weighted-average life (in years)	3 years 4 months 24 days	3 years 7 months 6 days
Key economic assumptions:
Prepayment speed assumption	18.00%	17.70%
Decrease in fair value from:
10% adverse change	$ 0	$ 1
25% adverse change	$ 1	$ 1
Discount rate assumption	14.10%	14.50%
Decrease in fair value from:
100 basis point increase	$ 0	$ 0
200 basis point increase	0	1
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	$ 752	$ 668
Expected weighted-average life (in years)	7 years 2 months 12 days	7 years
Decrease in fair value from:
Discount rate assumption	4.00%	4.30%
Decrease in fair value from:
100 basis point increase	$ 44	$ 37
200 basis point increase	$ 84	$ 72
Decrease in fair value from:
Credit loss assumption	3.80%	5.10%
Decrease in fair value from:
10% higher losses	$ 2	$ 2
25% higher losses	5	5
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	$ 304	$ 309
Expected weighted-average life (in years)	5 years	5 years 8 months 12 days
Decrease in fair value from:
Discount rate assumption	2.70%	3.70%
Decrease in fair value from:
100 basis point increase	$ 13	$ 14
200 basis point increase	$ 25	$ 28
Decrease in fair value from:
Credit loss assumption	0.00%	0.00%
Decrease in fair value from:
10% higher losses	$ 0	$ 0
25% higher losses	$ 0	$ 0