Goodwill and Other Intangible Assets - Identifiable Intangible Assets (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 4,472	$ 4,282
Accumulated Amortization	(1,304)	(1,140)
Net Carrying Amount	3,168	3,142
CDI
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	2,599	2,474
Accumulated Amortization	(485)	(365)
Net Carrying Amount	2,114	2,109
Other, primarily client relationship intangibles
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	1,873	1,808
Accumulated Amortization	(819)	(775)
Net Carrying Amount	$ 1,054	$ 1,033