Loans and Leases and the Allowance for Credit Losses - Summary of Payment Status of Loans Modified (Detail) - USD ($) $ in Thousands	Mar. 31, 2025	Mar. 31, 2024
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized cost	$ 1,292,000	$ 1,878,000
Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized cost	1,108,000	1,693,000
30-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized cost	117,000	121,000
Accruing Loans Past Due 90 Days or More
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized cost	67,000	64,000
Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized cost	313,000	327,000
Commercial and industrial | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized cost	293,000	310,000
Commercial and industrial | 30-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized cost	3,000	7,000
Commercial and industrial | Accruing Loans Past Due 90 Days or More
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized cost	17,000	10,000
Commercial Real Estate | Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized cost	468,000	772,000
Commercial Real Estate | Commercial | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized cost	419,000	715,000
Commercial Real Estate | Commercial | 30-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized cost	49,000	33,000
Commercial Real Estate | Commercial | Accruing Loans Past Due 90 Days or More
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized cost	0	24,000
Commercial Real Estate | Residential builder and developer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized cost	1,000	53,000
Commercial Real Estate | Residential builder and developer | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized cost	1,000	14,000
Commercial Real Estate | Residential builder and developer | 30-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized cost	0	39,000
Commercial Real Estate | Residential builder and developer | Accruing Loans Past Due 90 Days or More
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized cost	0	0
Commercial Real Estate | Other commercial construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized cost	328,000	539,000
Commercial Real Estate | Other commercial construction | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized cost	289,000	534,000
Commercial Real Estate | Other commercial construction | 30-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized cost	30,000	5,000
Commercial Real Estate | Other commercial construction | Accruing Loans Past Due 90 Days or More
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized cost	9,000	0
Residential Real Estate | Residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized cost	180,000	185,000
Residential Real Estate | Residential | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized cost	104,000	118,000
Residential Real Estate | Residential | 30-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized cost	35,000	37,000
Residential Real Estate | Residential | Accruing Loans Past Due 90 Days or More
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized cost	41,000	30,000
Consumer: | Home equity lines and loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized cost	1,000	2,000
Consumer: | Home equity lines and loans | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized cost	1,000	2,000
Consumer: | Home equity lines and loans | 30-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized cost	0	0
Consumer: | Home equity lines and loans | Accruing Loans Past Due 90 Days or More
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized cost	0	0
Consumer: | Recreational finance
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized cost	1,000	0
Consumer: | Recreational finance | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized cost	1,000	0
Consumer: | Recreational finance | 30-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized cost	0	0
Consumer: | Recreational finance | Accruing Loans Past Due 90 Days or More
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized cost	0	0
Consumer: | Automobile
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized cost	0	0
Consumer: | Automobile | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized cost	0	0
Consumer: | Automobile | 30-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized cost	0	0
Consumer: | Automobile | Accruing Loans Past Due 90 Days or More
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized cost	0	0
Consumer: | Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized cost	0	0
Consumer: | Other | Current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized cost	0	0
Consumer: | Other | 30-89 Days Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized cost	0	0
Consumer: | Other | Accruing Loans Past Due 90 Days or More
Accounts, Notes, Loans and Financing Receivable [Line Items]
Amortized cost	$ 0	$ 0