Goodwill and Other Intangible Assets - Identifiable Intangible Assets (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 4,282	$ 1,934
Accumulated Amortization	(1,140)	(1,176)
Net Carrying Amount	3,142	758
CDI
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	2,474	605
Accumulated Amortization	(365)	(460)
Net Carrying Amount	2,109	145
Other, primarily client relationship intangibles
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	1,808	1,329
Accumulated Amortization	(775)	(716)
Net Carrying Amount	$ 1,033	$ 613