Mortgage Servicing Rights - Estimated Fair Value (Details) - Mortgage Servicing Rights	Mar. 31, 2025	Mar. 31, 2024
Range of discount rates | Maximum
Mortgage Servicing Rights
Valuation assumptions	12.625	12.25
Range of discount rates | Minimum
Mortgage Servicing Rights
Valuation assumptions	9.625	9.75
Range of prepayment speeds | Maximum
Mortgage Servicing Rights
Valuation assumptions	3.75	2.82
Range of prepayment speeds | Minimum
Mortgage Servicing Rights
Valuation assumptions	0.91	0.86
Weighted average default rate
Mortgage Servicing Rights
Valuation assumptions	0.0106	0.0124