Significant Accounting Policies - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019		Dec. 31, 2018
Premises, Equipment and Capitalized Software Costs
Allowance for credit losses	$ 654	$ 835	$ 349		$ 238
Shareholders' equity	106,598	103,149	82,697
Retained Earnings
Premises, Equipment and Capitalized Software Costs
Shareholders' equity	$ 89,432	$ 78,694	70,589		64,175
Adjustment | Retained Earnings
Premises, Equipment and Capitalized Software Costs
Shareholders' equity			(100)	[1]	$ 63
Accounting Standards Update 2016-13 | Adjustment | Retained Earnings
Premises, Equipment and Capitalized Software Costs
Shareholders' equity			(100)
Accounting Standards Update 2016-13 | Adjustment | Allowance for Credit Losses
Premises, Equipment and Capitalized Software Costs
Allowance for credit losses			131
Accounting Standards Update 2016-13 | Adjustment | Allowance for Credit Losses on Employee Loans
Premises, Equipment and Capitalized Software Costs
Shareholders' equity			$ 124
Minimum
Premises, Equipment and Capitalized Software Costs
Effectiveness to benchmark interest rate (as a percent)	80.00%
Maximum
Premises, Equipment and Capitalized Software Costs
Effectiveness to benchmark interest rate (as a percent)	125.00%
Buildings
Premises, Equipment and Capitalized Software Costs
Estimated useful lives	39 years
Leasehold improvements—Building | Maximum
Premises, Equipment and Capitalized Software Costs
Estimated useful lives	25 years
Leasehold improvements—Other | Maximum
Premises, Equipment and Capitalized Software Costs
Estimated useful lives	15 years
Furniture and fixtures
Premises, Equipment and Capitalized Software Costs
Estimated useful lives	7 years
Computer and communications equipment | Minimum
Premises, Equipment and Capitalized Software Costs
Estimated useful lives	3 years
Computer and communications equipment | Maximum
Premises, Equipment and Capitalized Software Costs
Estimated useful lives	9 years
Power generation assets | Minimum
Premises, Equipment and Capitalized Software Costs
Estimated useful lives	15 years
Power generation assets | Maximum
Premises, Equipment and Capitalized Software Costs
Estimated useful lives	29 years
Capitalized software costs | Minimum
Premises, Equipment and Capitalized Software Costs
Estimated useful lives	2 years
Capitalized software costs | Maximum
Premises, Equipment and Capitalized Software Costs
Estimated useful lives	10 years

[1] See Note 2 for further information regarding cumulative adjustments for accounting changes.