Investment Securities (Securities Held to Maturity by Contractual Maturity) (Detail) $ in Thousands	Mar. 31, 2024 USD ($)
Investments, Debt and Equity Securities [Abstract]
Due in one year or less, amortized cost	$ 34,403
Due after one year through five years, amortized cost	181,204
Due after five years through ten years, amortized cost	114,993
Due after ten years, amortized cost	24,088
Amortized cost	354,688
Due in one year or less, fair value	34,210
Due after one year through five years, fair value	177,227
Due after five years through ten years, fair value	110,547
Due after ten years, fair value	19,475
Fair value	$ 341,459

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