Accounting Policies (Details) $ in Millions	12 Months Ended
	Dec. 31, 2020 USD ($) office	Dec. 31, 2019 USD ($)		Dec. 31, 2018 USD ($)		Jun. 30, 2020 USD ($)	Jan. 01, 2020 USD ($)	Dec. 31, 2017 USD ($)
Number of international offices | office	4
Stockholders' equity	$ 54,041	$ 49,343	[1]	$ 47,770	[1]			$ 47,585	[1]
Investment securities – held to maturity	1,441	17,661
Held-to-maturity securities, fair value	1,605	18,044
Other comprehensive income (loss), before tax and net of reclassifications into Net income	2,548	1,966		(739)
Securities available for sale debt securities, amortized cost	84,172	67,790
Investment securities – available for sale	$ 87,358	69,163
Total commercial lending | Charge off threshold - small business commercial loans of $100,000 Or Less
Threshold period of financing receivable past due, writeoff	180 days
Total commercial lending | Charge off threshold - smaller commercial leases of $1 Million or less
Threshold period of financing receivable past due, writeoff	120 days
Total commercial lending | Charge off threshold - small business credit card balances
Threshold period of financing receivable past due, writeoff	180 days
Total consumer lending | Charge off threshold - consumer loan
Threshold period of financing receivable past due, writeoff	180 days
Cumulative Effect, Period of Adoption, Adjustment
Stockholders' equity		(671)	[2]	62	[3]			(16)	[4]
Investment securities – held to maturity		(16,200)				$ (49)
Held-to-maturity securities, fair value		(16,500)				(48)
Other comprehensive income (loss), before tax and net of reclassifications into Net income		306
Securities available for sale debt securities, amortized cost		16,200				49	$ 16,200
Investment securities – available for sale		16,500				$ 48	$ 16,500
Minimum
Threshold period of financing receivable past due, writeoff	120 days
Minimum | Total consumer lending | Consumer loans and lines of credit, not secured by automobiles or residential real estate
Threshold period of financing receivable past due, writeoff	120 days
Minimum | Furniture and Equipment
Estimated useful life of property and equipment	1 year
Minimum | Software and Software Development Costs
Estimated useful life of property and equipment	1 year
Maximum
Threshold period of financing receivable past due, writeoff	180 days
Maximum | Total consumer lending | Consumer loans and lines of credit, not secured by automobiles or residential real estate
Threshold period of financing receivable past due, writeoff	180 days
Maximum | Furniture and Equipment
Estimated useful life of property and equipment	10 years
Maximum | Buildings
Estimated useful life of property and equipment	40 years
Maximum | Leasehold Improvements
Estimated useful life of property and equipment	15 years
Maximum | Software and Software Development Costs
Estimated useful life of property and equipment	10 years
Retained Earnings
Stockholders' equity	$ 46,848	42,215	[1]	38,919	[1]			35,481	[1]
Retained Earnings | Cumulative Effect, Period of Adoption, Adjustment
Stockholders' equity		$ (671)		$ 62	[3]			$ (22)	[4]

[1] The par value of our preferred stock outstanding was less than $0.5 million at each date and, therefore, is excluded from this presentation.

[2] Represents the impact of the adoption ASU 2016-13 - Financial Instruments - Credit Losses. See the Recently Adopted Accounting Standards portion of Note 1 Accounting Policies in this Report for additional detail on this adoption.

[3] Represents the impact of the adoption of ASU 2016-02 related primarily to deferred gains on previous sale-leaseback transactions.

[4] Represents the cumulative effect of adopting ASU 2014-09, ASU 2016-01, ASU 2017-12 and ASU 2018-02.