Goodwill and Other Intangible Assets - Identifiable Intangible Assets (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 1,923	$ 1,934
Accumulated Amortization	(1,197)	(1,176)
Net Carrying Amount	726	758
CDI
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	605	605
Accumulated Amortization	(471)	(460)
Net Carrying Amount	134	145
Other, primarily customer relationship intangibles
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	1,318	1,329
Accumulated Amortization	(726)	(716)
Net Carrying Amount	$ 592	$ 613