Goodwill and Other Intangible Assets - Summary Of Intangible Assets and Accumulated Amortization Included In The Consolidated Statements of Condition (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Intangible Assets [Line Items]
Gross Carrying Amount	$ 449	$ 241
Accumulated Amortization	(95)	(110)
Net Carrying Value	354	131
Core deposit intangibles
Intangible Assets [Line Items]
Gross Carrying Amount	371	157
Accumulated Amortization	(81)	(47)
Net Carrying Value	290	110
Client relationships
Intangible Assets [Line Items]
Gross Carrying Amount	37	78
Accumulated Amortization	(8)	(60)
Net Carrying Value	29	18
Other
Intangible Assets [Line Items]
Gross Carrying Amount	41	6
Accumulated Amortization	(6)	(3)
Net Carrying Value	$ 35	$ 3