Lease Transactions (Narrative) (Detail) - JPY (¥) ¥ in Millions |
12 Months Ended | |
|---|---|---|
Mar. 31, 2026 |
Mar. 31, 2025 |
|
| Leases [Abstract] | ||
| Right-of-use assets of finance leases, in consolidated balance sheets line item | Premises and equipment—net (Notes 5 and 7) | Premises and equipment—net (Notes 5 and 7) |
| Right-of-use assets of finance leases | ¥ 23,137 | ¥ 21,035 |
| Lease liabilities of finance leases, in consolidated balance sheets line item | Long-term debt (including ¥153,742 and ¥79,698 measured at fair value under the fair value option in 2025 and 2026) (Notes 7, 9, 12 and 31) | Long-term debt (including ¥153,742 and ¥79,698 measured at fair value under the fair value option in 2025 and 2026) (Notes 7, 9, 12 and 31) |
| Lease liabilities of finance leases | ¥ 26,088 | ¥ 21,460 |
| Right-of-use assets of operating leases, in consolidated balance sheets line item | Other Assets | Other Assets |
| Right-of-use assets of operating leases | ¥ 282,736 | ¥ 247,221 |
| Lease liabilities of operating leases, in consolidated balance sheets line item | Other Liabilities | Other Liabilities |
| Amount on balance sheet | ¥ 370,365 | ¥ 341,499 |
| Operating Lease, Impairment Loss | 15,968 | 19,520 |
| Property, plant, and equipment separately for underlying assets under operating leases from owned assets subject to operating leases are carrying amount as | ¥ 280,099 | ¥ 142,964 |