Goodwill and Other Intangible Assets - Gross Carrying Amount and Accumulated Amortization of Intangible Assets (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Goodwill [Line Items]
Gross Carrying Amount	$ 663	$ 741
Accumulated Amortization	347	325
Core Deposit Intangibles [Member]
Goodwill [Line Items]
Gross Carrying Amount	396	461
Accumulated Amortization	184	192
Purchased Credit Card Relationship Intangible [Member]
Goodwill [Line Items]
Gross Carrying Amount	152	152
Accumulated Amortization	138	126
Other Intangible Assets [Member]
Goodwill [Line Items]
Gross Carrying Amount	115	128
Accumulated Amortization	$ 25	$ 7