Basis of Financial Statements and Summary of Significant Accounting Policies (Estimated Useful Lives of Premises and Equipment) (Detail) |
Mar. 31, 2025 |
|---|---|
| Buildings | Minimum | |
| Property, Plant and Equipment [Line Items] | |
| Premises and equipment, Useful life, years | 15 years |
| Buildings | Maximum | |
| Property, Plant and Equipment [Line Items] | |
| Premises and equipment, Useful life, years | 50 years |
| Equipment and furniture | Minimum | |
| Property, Plant and Equipment [Line Items] | |
| Premises and equipment, Useful life, years | 2 years |
| Equipment and furniture | Maximum | |
| Property, Plant and Equipment [Line Items] | |
| Premises and equipment, Useful life, years | 20 years |
| Leasehold improvements | Minimum | |
| Property, Plant and Equipment [Line Items] | |
| Premises and equipment, Useful life, years | 4 years |
| Leasehold improvements | Maximum | |
| Property, Plant and Equipment [Line Items] | |
| Premises and equipment, Useful life, years | 50 years |