Business Acquisitions (USAA-IMCO Narrative) (Details) account in Millions, $ in Millions		3 Months Ended		4 Months Ended	9 Months Ended		12 Months Ended
	May 26, 2020 USD ($) account	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)
Business Acquisition [Line Items]
Goodwill		$ 1,737		$ 1,737	$ 1,737		$ 1,227
USAA-IMCO [Member]
Business Acquisition [Line Items]
Purchase price	$ 1,581
Number of brokerage and managed portfolio accounts acquired | account	1,000,000
Client assets acquired	$ 80,000
Adjustment to intangible assets		9
Adjustment to purchase price		43
Adjustment to goodwill		34
Intangible assets acquired	1,109
Goodwill	$ 472
Net revenue		99		138
Net loss		$ 4		$ 41
Termination fee					20
Acquisition costs			$ 4		52	$ 7
After-tax acquisition and integration-related costs					$ 39		$ 10