Retirement Benefits - Effect of the Asset Ceiling (Detail) - JPY (¥) ¥ in Millions	12 Months Ended
Mar. 31, 2026	Mar. 31, 2025
Disclosure of net defined benefit liability (asset) [abstract]
At beginning of period	¥ 443,867	¥ 330,739
Interest cost	9,943	4,896
Change in the asset ceiling	205,920	108,232
At end of period	¥ 659,730	¥ 443,867

The amount of deficit or surplus in a defined benefit plan, adjusted for any effect of limiting a net defined benefit asset to the asset ceiling. [Refer: Defined benefit plans [domain]]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Note Effective 2027-01-01
-Name IFRS
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Note Effective 2027-01-01
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