Name:	ifrs-full_AmountsSubjectToEnforceableMasterNettingArrangementOrSimilarAgreementNotSetOffAgainstFinancialLiabilitiesAbstract
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

The amount of cash collateral pledged that is subject to an enforceable master netting arrangement or similar agreement and that is not set off against financial liabilities. [Refer: Financial liabilities]

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Name IFRS
-Number 7
-IssueDate 2023-01-01
-Paragraph IG40D
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=7&code=ifrs-tx-2023-en-r&anchor=para_IG40D&doctype=Implementation%20Guidance
-URIDate 2023-03-23

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Name IFRS
-Number 7
-IssueDate 2023-01-01
-Paragraph 13C
-Subparagraph d
-Clause ii
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=7&code=ifrs-tx-2023-en-r&anchor=para_13C_d_ii&doctype=Standard
-URIDate 2023-03-23

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

The amount of cash collateral received that is subject to an enforceable master netting arrangement or similar agreement and that is not set off against financial assets. [Refer: Financial assets]

Name:	ifrs-full_CashCollateralReceivedSubjectToEnforceableMasterNettingArrangementOrSimilarAgreementNotSetOffAgainstFinancialAssets
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

The amount of financial instruments subject to an enforceable master netting arrangement or similar agreement that are not set off against financial assets. [Refer: Financial assets]

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Name IFRS
-Number 7
-IssueDate 2023-01-01
-Paragraph IG40D
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=7&code=ifrs-tx-2023-en-r&anchor=para_IG40D&doctype=Implementation%20Guidance
-URIDate 2023-03-23

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Name IFRS
-Number 7
-IssueDate 2023-01-01
-Paragraph 13C
-Subparagraph d
-Clause i
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=7&code=ifrs-tx-2023-en-r&anchor=para_13C_d_i&doctype=Standard
-URIDate 2023-03-23

Name:	ifrs-full_FinancialInstrumentsSubjectToEnforceableMasterNettingArrangementOrSimilarAgreementNotSetOffAgainstFinancialAssets
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

The amount of financial instruments subject to an enforceable master netting arrangement or similar agreement that are not set off against financial liabilities. [Refer: Financial liabilities]

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Name IFRS
-Number 7
-IssueDate 2023-01-01
-Paragraph IG40D
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=7&code=ifrs-tx-2023-en-r&anchor=para_IG40D&doctype=Implementation%20Guidance
-URIDate 2023-03-23

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Name IFRS
-Number 7
-IssueDate 2023-01-01
-Paragraph 13C
-Subparagraph d
-Clause i
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=7&code=ifrs-tx-2023-en-r&anchor=para_13C_d_i&doctype=Standard
-URIDate 2023-03-23

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

The amount of financial assets set off against financial liabilities when an entity: (a) currently has a legally enforceable right to set off the recognised amounts; and (b) intends either to settle on a net basis, or to realise the asset and settle the liability simultaneously. [Refer: Financial assets; Financial liabilities]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 7
-IssueDate 2023-01-01
-Paragraph 13C
-Subparagraph b
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=7&code=ifrs-tx-2023-en-r&anchor=para_13C_b&doctype=Standard
-URIDate 2023-03-23

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

The gross amount of recognised financial assets that are subject either to offsetting or to an enforceable master netting arrangement or similar agreement. [Refer: Financial assets]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 7
-IssueDate 2023-01-01
-Paragraph 13C
-Subparagraph a
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=7&code=ifrs-tx-2023-en-r&anchor=para_13C_a&doctype=Standard
-URIDate 2023-03-23

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

The amount of financial liabilities set off against financial assets when an entity: (a) currently has a legally enforceable right to set off the recognised amounts; and (b) intends either to settle on a net basis or to realise the asset and settle the liability simultaneously. [Refer: Financial assets; Financial liabilities]

Name:	ifrs-full_GrossFinancialLiabilitiesSetOffAgainstFinancialAssetsSubjectToOffsettingEnforceableMasterNettingArrangementsOrSimilarAgreements
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

The gross amount of recognised financial liabilities that are subject either to offsetting or to an enforceable master netting arrangement or similar agreement. [Refer: Financial liabilities]

Name:	ifrs-full_GrossFinancialLiabilitiesSubjectToOffsettingEnforceableMasterNettingArrangementsOrSimilarAgreements
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

The amount remaining after deducting the amounts subject to an enforceable master netting arrangement or similar agreement that were not set off against financial assets, from the net amount of financial assets subject to offsetting or subject to an enforceable master netting arrangement or similar agreement presented in the statement of financial position.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 7
-IssueDate 2023-01-01
-Paragraph 13C
-Subparagraph e
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=7&code=ifrs-tx-2023-en-r&anchor=para_13C_e&doctype=Standard
-URIDate 2023-03-23

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

- References

No definition available.

Name:	ifrs-full_NetFinancialAssetsSubjectToOffsettingEnforceableMasterNettingArrangementsOrSimilarAgreementsAbstract
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

The net amount of financial assets that are subject either to offsetting or to an enforceable master netting arrangement or similar agreement, presented in the statement of financial position. [Refer: Financial assets]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 7
-IssueDate 2023-01-01
-Paragraph 13C
-Subparagraph c
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=7&code=ifrs-tx-2023-en-r&anchor=para_13C_c&doctype=Standard
-URIDate 2023-03-23

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

The amount remaining after deducting the amounts subject to an enforceable master netting arrangement or similar agreement that were not set off against financial liabilities, from the net amount of financial liabilities subject to offsetting or subject to an enforceable master netting arrangement or similar agreement presented in the statement of financial position.

Name:	ifrs-full_NetFinancialLiabilitiesSubjectToOffsettingEnforceableMasterNettingArrangementsOrSimilarAgreements
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- References

No definition available.

Name:	ifrs-full_NetFinancialLiabilitiesSubjectToOffsettingEnforceableMasterNettingArrangementsOrSimilarAgreementsAbstract
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

The net amount of financial liabilities that are subject either to offsetting or to an enforceable master netting arrangement or similar agreement, presented in the statement of financial position. [Refer: Financial liabilities]

Name:	ifrs-full_NetFinancialLiabilitiesSubjectToOffsettingEnforceableMasterNettingArrangementsOrSimilarAgreementsInStatementOfFinancialPosition
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Amounts Subject To Enforceable Master Netting Arrangement Or Similar Agreement Not Set Off Against Financial Assets (Liabilities) [Abstract]

No definition available.

Name:	nggtf_AmountsSubjectToEnforceableMasterNettingArrangementOrSimilarAgreementNotSetOffAgainstFinancialAssetsLiabilitiesAbstract
Namespace Prefix:	nggtf_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Cash Collateral Pledged Subject To Enforceable Master Netting Agreement Or Similar Agreement Not Set Off Against Financial Assets (Liabilities)

No definition available.

Name:	nggtf_CashCollateralPledgedSubjectToEnforceableMasterNettingAgreementOrSimilarAgreementNotSetOffAgainstFinancialAssetsLiabilities
Namespace Prefix:	nggtf_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Financial Instruments Subject Enforceable Master Netting Arrangement Or Similar Agreement Not Set Off Against Financial Assets (Liabilities)

No definition available.

Name:	nggtf_FinancialInstrumentsSubjectEnforceableMasterNettingArrangementOrSimilarAgreementNotSetOffAgainstFinancialAssetsLiabilities
Namespace Prefix:	nggtf_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Gross Financial Assets (Liabilities) Subject To Offsetting, Enforceable Master Netting Arrangements Or Similar Agreements

No definition available.

Name:	nggtf_GrossFinancialAssetsLiabilitiesSubjectToOffsettingEnforceableMasterNettingArrangementsOrSimilarAgreements
Namespace Prefix:	nggtf_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Gross Financial Liabilities (Assets) Set Off Against Financial Assets (Liabilities) Subject To Offsetting, Enforceable Master Netting Arrangements Or Similar Agreements

No definition available.

Name:	nggtf_GrossFinancialLiabilitiesAssetsSetOffAgainstFinancialAssetsLiabilitiesSubjectToOffsettingEnforceableMasterNettingArrangementsOrSimilarAgreements
Namespace Prefix:	nggtf_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Net Financial Assets (Liabilities) Subject To Offsetting, Enforceable Master Netting Agreements Or Similar Agreements In Statements Of Financial Position

No definition available.

Name:	nggtf_NetFinancialAssetsLiabilitiesSubjectToOffsettingEnforceableMasterNettingAgreementsOrSimilarAgreementsInStatementsOfFinancialPosition
Namespace Prefix:	nggtf_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Net Financial Assets (Liabilities) Subject To Offsetting, Enforceable Master Netting Arrangements Or Similar Agreements

No definition available.

Name:	nggtf_NetFinancialAssetsLiabilitiesSubjectToOffsettingEnforceableMasterNettingArrangementsOrSimilarAgreements
Namespace Prefix:	nggtf_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Net Financial Assets (Liabilities) Subject to Offsetting, Enforceable Master Netting Arrangements Or Similar Agreements [Abstract]

No definition available.

Name:	nggtf_NetFinancialAssetsLiabilitiesSubjectToOffsettingEnforceableMasterNettingArrangementsOrSimilarAgreementsAbstract
Namespace Prefix:	nggtf_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Name:	ifrs-full_TypesOfRisksAxis=ifrs-full_CreditRiskMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	ifrs-full_ClassesOfFinancialLiabilitiesAxis=nggtf_FinancingDerivativesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	ifrs-full_ClassesOfFinancialLiabilitiesAxis=nggtf_CommodityDerivativesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	ifrs-full_ClassesOfFinancialAssetsAxis=nggtf_FinancingDerivativesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: