Investment Securities - Summary of Carrying Value of Held-to-Maturity Securities (Detail) - USD ($) $ in Thousands	Jun. 30, 2025	Dec. 31, 2024
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Line Items]
Held-to-maturity securities pledged	$ 7,799,924	$ 8,237,273
Pledged for deposits
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Line Items]
Held-to-maturity securities pledged	1,760,751	1,978,445
Pledged for borrowings and other
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Line Items]
Held-to-maturity securities pledged	$ 6,039,173	$ 6,258,828