Accounting and Reporting Developments (Details) - USD ($) $ in Millions		6 Months Ended
	Jan. 01, 2020	Jun. 30, 2019	Jun. 30, 2020		Mar. 31, 2020	Dec. 31, 2019		Mar. 31, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
ALLL and reserve for unfunded commitments	$ 33	$ 1,115	$ 2,696	[1]	$ 2,348	$ 1,202	[1]	$ 1,115	$ 1,103
Impact of cumulative effect of change in accounting principles			17,643			$ 18,315
Carrying value of loans and leases evaluated for ALLL			$ 1
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201613Member	us-gaap:AccountingStandardsUpdate201602Member
Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
ALLL and reserve for unfunded commitments	$ 653
Impact of cumulative effect of change in accounting principles	472
Amount of ALLL on purchased financial assets	$ 33

[1] Includes $66 and $74 of other short-term investments, $1,032 and $1,354 of portfolio loans and leases, $(14) and $(7) of ALLL, $7 and $8 of other assets, $2 and $2 of other liabilities, and $933 and $1,253 of long-term debt from consolidated VIEs that are included in their respective captions above at June 30, 2020 and December 31, 2019, respectively. For further information refer to Note 13.