Goodwill and Acquired Intangible Assets (Changes in Carrying Amount of Goodwill as Allocated to Reportable Segments) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020		Dec. 31, 2019
Goodwill [Roll Forward]
Beginning balance		$ 1,227	[1]	$ 1,227
Goodwill acquired and other changes during the period				0
Goodwill acquired		510
Ending balance	[1]	11,952		1,227
TD Ameritrade [Member]
Goodwill [Roll Forward]
Goodwill acquired		10,215
Investor Services [Member]
Goodwill [Roll Forward]
Beginning balance		1,096		1,096
Goodwill acquired and other changes during the period				0
Goodwill acquired		494
Ending balance		7,970		1,096
Investor Services [Member] | TD Ameritrade [Member]
Goodwill [Roll Forward]
Goodwill acquired		6,380
Advisor Services [Member]
Goodwill [Roll Forward]
Beginning balance		131		131
Goodwill acquired and other changes during the period				0
Goodwill acquired		16
Ending balance		3,982		$ 131
Advisor Services [Member] | TD Ameritrade [Member]
Goodwill [Roll Forward]
Goodwill acquired		$ 3,835

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