Low Income housing tax credit - Summary of Affordable Housing Tax Credit Investment and Related Unfunded Commitment (Details) - USD ($) $ in Thousands	12 Months Ended
Mar. 31, 2026	Mar. 31, 2025
Investments in Affordable Housing Projects [Abstract]
Affordable housing tax credit investments - beginning of year	$ 1,313	$ 1,479
Investment, Proportional Amortization Method, Elected, Statement of Financial Position [Extensible Enumeration]	Other Assets	Other Assets
Less: amortization	$ (173)	$ (166)
Net affordable housing tax credit investments - end of year	1,140	1,313
Unfunded commitments	276	487
Tax credits and other tax benefits recognized	172	164
Proportional amortization expense included in income tax expense	$ (173)	$ (166)
Investment Program, Proportional Amortization Method, Applied, Amortization Expense, Statement of Income or Comprehensive Income [Extensible Enumeration]	Income Tax Expense (Benefit)	Income Tax Expense (Benefit)
Investment Program, Proportional Amortization Method, Applied, Amortization Expense, Statement of Cash Flows [Extensible Enumeration]	Deferred Income Tax Expense (Benefit)	Deferred Income Tax Expense (Benefit)

Amount of amortization of investment for the year in qualified affordable housing projects.

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Amount of net investment in qualified affordable housing projects.

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Investment program proportional amortization method elected income tax credit and other income tax benefit before amortization statement of income or comprehensive income extensible enumeration not disclosed flag.

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Amount of investment that generates income tax credit and other income tax benefit under tax credit program elected to be accounted for using proportional amortization method. Includes, but is not limited to, investment under program not meeting condition for accounting under proportional amortization method.

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Amount of commitment and contingent commitment, including amount of delayed equity contribution, for investment that generates income tax credit and other income tax benefit under tax credit program elected to be accounted for using proportional amortization method. Includes, but is not limited to, commitment and contingent commitment related to investment under tax credit program not meeting condition for accounting under proportional amortization method.

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