Investment Securities - Additional Information (Detail) - JPY (¥) ¥ in Millions	12 Months Ended
Mar. 31, 2026	Mar. 31, 2025
Disclosure of detailed information about financial instruments [abstract]
Transfer to retained earnings from disposal of equity instruments at fair value through other reserves	¥ 330,163	¥ 338,766

The amount of transfers within equity of the cumulative gain (loss) on financial liabilities designated as at fair value through profit or loss for which changes in the liability's credit risk are presented in other comprehensive income. [Refer: Financial liabilities at fair value through profit or loss]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 7
-IssueDate 2025-01-01
-Paragraph 10
-Subparagraph c
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=7&code=ifrs-tx-2025-en-r&anchor=para_10_c&doctype=Standard
-URIDate 2025-03-27

Name:	ifrs-full_TransfersOfCumulativeGainLossWithinEquity
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration