Investment Securities - Additional Information (Detail)	3 Months Ended		9 Months Ended
	Sep. 30, 2023 USD ($) Security	Sep. 30, 2022 USD ($)	Sep. 30, 2023 USD ($) Security	Sep. 30, 2022 USD ($)	Dec. 31, 2022 USD ($)
Summary of Investment Holdings [Line Items]
Gross realized gains(loss) on sale of investment securities	$ 0	$ 0	$ 0	$ 0
Gains (losses) on equity securities	$ (235,000)	$ (1,108,000)	$ 353,000	$ (1,913,000)
Number of debt securities with aggregate gross unrealized losses | Security	4,279		4,279
Unrealized losses on individual debt securities			$ (2,300,000,000)
Cost method equity securities	$ 913,000,000		913,000,000
Investment securities pledged to secure debt carrying value	8,200,000,000		8,200,000,000		$ 7,900,000,000
Carrying value of investment securities pledged related to repurchase transactions	696,000,000		696,000,000		567,000,000
Available-for-Sale Securities [Member]
Summary of Investment Holdings [Line Items]
Allowance for credit losses	$ 0		$ 0		$ 0