Securities Available for Sale and Held to Maturity - Additional Information (Details) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023	Dec. 31, 2022
Schedule of Available For Sale and Held to Maturity Securities [Line Items]
Reclassification of Securities available for sale to securities held to maturity				$ 766,000,000
Net unrealized holding loss on AFS Securities at date of transfer				91,900,000
Net unrealized holding losses on AFS Securities, net of tax at date of transfer				$ 68,900,000
Net unamortized, unrealized loss on transfer of securities	$ 54,800,000		$ 57,600,000
Credit loss recognized	0		0
Potential credit loss exposure	340,000		340,000
Securities held to maturity	1,415,025,000		1,426,279,000
Gross realized losses	0	$ 0
Gross realized gains	0	$ 0
Pledged to collateralize public deposits and securities sold under repurchase agreements and for other purposes as permitted by law	2,291,000,000		2,321,000,000
Pledged securities providing additional contingency funding	0		0
30 Days or More Past Due [Member]
Schedule of Available For Sale and Held to Maturity Securities [Line Items]
Securities held to maturity	0		0
Securities Available for Sale [Member]
Schedule of Available For Sale and Held to Maturity Securities [Line Items]
Accrued interest receivable	3,700,000		3,700,000
Securities Held to Maturity [Member]
Schedule of Available For Sale and Held to Maturity Securities [Line Items]
Accrued interest receivable	2,700,000		2,600,000
Reserve for credit loss	0		0
Held-to-maturity nonnaccrual	$ 0		$ 0