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, 2023		Dec. 31, 2022
Goodwill [Roll Forward]
Beginning balance		$ 11,951	[1]	$ 11,952
Goodwill acquired and other changes during the period		0		(1)
Ending balance	[1]	11,951		11,951
Investor Services
Goodwill [Roll Forward]
Beginning balance		7,969		7,970
Goodwill acquired and other changes during the period		0		(1)
Ending balance		7,969		7,969
Advisor Services
Goodwill [Roll Forward]
Beginning balance		3,982		3,982
Goodwill acquired and other changes during the period		0		0
Ending balance		$ 3,982		$ 3,982

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