Goodwill and Other Intangible Assets - Summary of Intangible Assets and Accumulated Amortization Included in the Consolidated Statements of Condition (Details) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Intangible Assets [Line Items]
Gross Carrying Amount	$ 430	$ 430
Accumulated Amortization	(208)	(196)
Net Carrying Value	222	234
Core deposit intangibles
Intangible Assets [Line Items]
Gross Carrying Amount	371	371
Accumulated Amortization	(181)	(171)
Net Carrying Value	190	200
Client relationships
Intangible Assets [Line Items]
Gross Carrying Amount	32	32
Accumulated Amortization	(14)	(13)
Net Carrying Value	18	19
Other
Intangible Assets [Line Items]
Gross Carrying Amount	27	27
Accumulated Amortization	(13)	(12)
Net Carrying Value	$ 14	$ 15