Investment Securities - Amortized Cost and Estimated Fair Value of Debt Securities by Contractual Maturity (Detail) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Debt securities available for sale:
Due in one year or less	$ 5,023
Due after one year through five years	2,921
Due after five years through ten years	50
Total available for sale (amortized cost)	7,994
Mortgage-backed securities	2,697
Investment securities available for sale, amortized cost	10,691	$ 11,193
Debt securities held to maturity:
Due in one year or less	15
Due after one year through five years	1,179
Due after five years through ten years	1,351
Due after ten years	963
Total available for held to maturity (amortized cost)	3,508
Mortgage-backed securities	11,822
Amortized cost for held to maturity	15,330	13,530
Debt securities available for sale:
Due in one year or less	4,970
Due after one year through five years	2,856
Due after five years through ten years	44
Total available for sale (fair value)	7,870
Mortgage-backed securities	2,570
Total	10,440	10,749
Debt securities held to maturity:
Due in one year or less	14
Due after one year through five years	1,147
Due after five years through ten years	1,327
Due after ten years	922
Total available for held to maturity (fair value)	3,410
Mortgage-backed securities	10,898
Total	$ 14,308	$ 12,375