Investment Securities - Additional Information (Detail)	3 Months Ended		9 Months Ended
	Sep. 30, 2024 USD ($) security	Sep. 30, 2023 USD ($)	Sep. 30, 2024 USD ($) security	Sep. 30, 2023 USD ($)	Dec. 31, 2023 USD ($)
Summary of Investment Holdings [Line Items]
Gross realized gains(loss) on sale of investment securities			$ 13,000,000	$ 0
Gains (losses) on equity securities	$ (2,000,000)	$ 0	$ (8,000,000)	$ 0
Number of debt securities with aggregate gross unrealized losses | security	3,600		3,600
Unrealized losses on individual debt securities			$ 923,000,000
Cost method equity securities	$ 840,000,000		840,000,000
Allowance for credit losses	0		0		$ 0
Investment securities pledged to secure debt carrying value	7,400,000,000		7,400,000,000		8,200,000,000
Carrying value of investment securities pledged related to repurchase transactions	$ 124,000,000		$ 124,000,000		$ 393,000,000