Mortgage Banking Activities, Economic Assumptions and Sensitivity of Residential MSRs (Details) - Residential mortgage servicing rights [Member] $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2022 USD ($) $ / loan	Dec. 31, 2021 USD ($) $ / loan	Mar. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
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]
Mortgage servicing rights, carried at fair value	$ 8,511	$ 6,920	$ 7,536	$ 6,125
Expected weighted-average life (in years)	5 years 8 months 12 days	4 years 8 months 12 days
Assumption For Fair Value Of Assets Or Liabilities That Relate To Transferor's Continuing Involvement, Key Economic Assumptions [Abstract]
Prepayment rate assumption	11.10%	14.70%
Impact on fair value from 10% adverse change	$ 339	$ 356
Impact on fair value from 25% adverse change	$ 803	$ 834
Discount rate assumption	7.40%	6.40%
Impact on fair value from 100 basis point increase	$ 337	$ 276
Impact on fair value from 200 basis point increase	$ 646	$ 529
Cost to service assumption ($ per loan) | $ / loan	102	106
Impact on fair value from 10% adverse change	$ 177	$ 165
Impact on fair value from 25% adverse change	$ 441	$ 411