Goodwill and Other Intangible Assets - Identifiable Intangible Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Intangible Assets
Amortization Expense	$ 34	$ 26	$ 30
Gross Carrying Amount	931	932
Accumulated Amortization	(670)	(647)
Net Carrying Amount	261	285
Core deposit intangibles
Intangible Assets
Gross Carrying Amount	565	565
Accumulated Amortization	(543)	(537)
Net Carrying Amount	22	28
Trade names
Intangible Assets
Gross Carrying Amount	115	111
Accumulated Amortization	(35)	(32)
Net Carrying Amount	80	79
Customer Relationships
Intangible Assets
Gross Carrying Amount	238	238
Accumulated Amortization	(79)	(63)
Net Carrying Amount	159	175
Other intangibles assets
Intangible Assets
Gross Carrying Amount	13	18
Accumulated Amortization	(13)	(15)
Net Carrying Amount	$ 0	$ 3