Securities - Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023	Dec. 31, 2022
Schedule of Trading Securities and Other Trading Assets [Line Items]
Proceeds from sales of securities available for sale	$ 19,153,000	$ 68,000
Gross realized gains from securities	139,000	0
Gross realized losses from securities	0	2,000
Accrued interest on securities available for sale	30,300,000		$ 31,600,000
Impairment on one corporate available-for-sale security		4,800,000
ACL related to AFS Securities	0		0
Sales of securities held to maturity	0	0
Amortized cost of available for sale securities transferred to held to maturity				$ 4,100,000,000
Fair value of available for sale securities transferred to held to maturity				$ 3,800,000,000
Gain (loss) on transfer of securities	0
Unamortized unrealized loss	198,400,000
Accrued interest on securities held to maturity	24,000,000.0		27,200,000
Unrealized gain (loss) on trading securities	40,000	$ 0
Securities sold not yet purchased	11,700,000		8,000,000
Collateral Pledged [Member] | U.S. Government and Other Public Deposit [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Pledged securities for deposits	$ 9,400,000,000		$ 10,100,000,000