Goodwill and Other Intangible Assets - Total Amortizing Intangible Assets (Detail) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 261	$ 261
Accumulated Amortization	167	114
Net Carrying Amount	94	147
Core deposit
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	218	218
Accumulated Amortization	131	90
Net Carrying Amount	87	128
Other
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	43	43
Accumulated Amortization	36	24
Net Carrying Amount	$ 7	$ 19