Investment Securities - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2025 USD ($) security	Mar. 31, 2024 USD ($)	Dec. 31, 2024 USD ($)
Summary of Investment Holdings [Line Items]
Gross realized gains (loss) on sale of investment securities	$ 0	$ 0
Gains (losses) on equity securities	$ 0	$ 2,000,000
Number of debt securities with aggregate gross unrealized losses | security	3,597
Unrealized losses on individual debt securities	$ 1,200,000,000
Cost method equity securities	706,000,000
Allowance for credit losses	0		$ 0
Investment securities pledged to secure debt carrying value	6,100,000,000		6,200,000,000
Carrying value of investment securities pledged related to repurchase transactions	$ 71,000,000		$ 71,000,000