Employee Incentive, Retirement, Deferred Compensation, and Career Achievement Plans (Stock-Based Compensation Expense and Related Income Tax Benefit) (Details) - USD ($) $ in Millions			12 Months Ended
		Oct. 06, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total share-based compensation expense	[1]		$ 204	$ 183	$ 197
Income tax benefit on share-based compensation expense			(49)	(44)	(47)
Income tax benefit/(expense)	[2]		(1,001)	(1,144)	(1,055)
TD Ameritrade [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Conversion of shares (in shares)		1.0837
Fair value of replaced TD Ameritrade equity awards attributable to pre-combination services		$ 94
Remaining portion of value		$ 73
Period for recognition		1 year 10 months 24 days
Accounting Standards Update 2016-09 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Income tax benefit/(expense)			$ 14	23	46
Stock option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Period for recognition			10 months 24 days
Total share-based compensation expense			$ 36	51	51
Restricted stock unit [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Period for recognition			2 years 2 months 12 days
Total share-based compensation expense			$ 156	120	136
Restricted stock unit [Member] | Non-Officer Employee [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total share-based compensation expense					36
Employee stock purchase plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total share-based compensation expense			$ 12	$ 12	$ 10

[1] Certain prior year amounts have been reclassified to conform to the current year presentation. See Note 1 for additional information.

[2] Certain prior year amounts have been reclassified to conform to the current year presentation. See Note 1 for additional information.