Summary of Significant Accounting and Reporting Policies - Accounting Standards (Details) - USD ($) $ in Millions		12 Months Ended
	Jan. 01, 2020	Dec. 31, 2020		Dec. 31, 2019		Dec. 31, 2018	Dec. 31, 2017
New Accounting Pronouncement, Early Adoption [Line Items]
ALLL and reserve for unfunded commitments	$ 653	$ 2,453	[1]	$ 1,202	[1]	$ 1,103	$ 1,196
Equity		23,111		21,203		16,250	16,220
Increase in purchased financial assets with credit deterioration	33
Retained Earnings
New Accounting Pronouncement, Early Adoption [Line Items]
Equity				18,315		16,578	14,957
Cumulative Effect, Period of Adoption, Adjustment
New Accounting Pronouncement, Early Adoption [Line Items]
Equity				(472)	[2]	10	4
Increase in purchased financial assets with credit deterioration		$ 643
Cumulative Effect, Period of Adoption, Adjustment | Retained Earnings
New Accounting Pronouncement, Early Adoption [Line Items]
Equity	$ 472			$ (472)	[2]	$ 10	$ 6

[1] Includes $55 and $74 of other short-term investments, $756 and $1,354 of portfolio loans and leases, $(7) and $(7) of ALLL, $5 and $8 of other assets, $2 and $2 of other liabilities and $656 and $1,253 of long-term debt from consolidated VIEs that are included in their respective captions above at December 31, 2020 and 2019, respectively. For further information, refer to Note 13.

[2] Related to the adoption of ASU 2016-13 as of January 1, 2020. Refer to Note 1 for additional information.