Investment Securities - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2024 USD ($) security	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)
Summary of Investment Holdings [Line Items]
Gross realized gains (loss) on sale of investment securities		$ 0	$ 0
Number of securities | security	3,820
Unrealized losses on individual debt securities	$ 1,500,000,000
Cost method equity securities	772,000,000
Allowance for credit losses	0	0
Investment securities, pledged as collateral for public deposits	6,200,000,000	8,200,000,000
Debt Securities, Available-for-Sale, Realized Gain	27,000,000
Debt Securities, Available-for-Sale, Realized Loss	15,000,000
Repurchase Transactions
Summary of Investment Holdings [Line Items]
Investment securities, pledged as collateral for public deposits	$ 71,000,000	$ 393,000,000