Goodwill and Other Intangible Assets - Identifiable Intangible Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 1,934	$ 1,816
Accumulated Amortization	(1,176)	(1,105)
Net Carrying Amount	$ 758	711
CDI
Acquired Finite-Lived Intangible Assets [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	6 years 2 months 12 days
Gross Carrying Amount	$ 605	605
Accumulated Amortization	(460)	(409)
Net Carrying Amount	$ 145	196
Other, primarily customer relationship intangibles
Acquired Finite-Lived Intangible Assets [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	11 years 9 months 18 days
Gross Carrying Amount	$ 1,329	1,211
Accumulated Amortization	(716)	(696)
Net Carrying Amount	$ 613	$ 515