Derivative instruments and hedging activities - Summary of Fair Value Hedges (Detail) - Fair value hedges [member] - Fixed rate bonds [member] ¥ in Millions	Mar. 31, 2025 JPY (¥)
Derivative Instruments And Hedging Activities [Line Items]
Carrying amount of hedged items asset	¥ 485,960
Accumulative fair value hedge adjustments asset	¥ (3,330)

The accumulated amount of fair value hedge adjustment on a hedged item that is included in the carrying amount of the hedged item, recognised in the statement of financial position as an asset. [Refer: Hedged items [domain]]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 7
-IssueDate 2025-01-01
-Paragraph 24B
-Subparagraph a
-Clause ii
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=7&code=ifrs-tx-2025-en-r&anchor=para_24B_a_ii&doctype=Standard
-URIDate 2025-03-27

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Note Effective 2027-01-01
-Name IFRS
-Number 19
-IssueDate 2025-01-01
-Paragraph 61
-Subparagraph a
-Clause ii
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=19&code=ifrs-tx-2025-en-r&anchor=para_61_a_ii&doctype=Standard
-URIDate 2025-03-27

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Note Effective 2027-01-01
-Name IFRS
-Number 19
-IssueDate 2025-01-01
-Paragraph 61
-Subparagraph a
-Clause ii
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=19&code=ifrs-tx-2025-en-r&anchor=para_61_a_ii&doctype=Standard
-URIDate 2025-03-27

Name:	ifrs-full_AccumulatedFairValueHedgeAdjustmentOnHedgedItemIncludedInCarryingAmountAssets
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant