Name:	ifrs-full_TradeAndOtherReceivablesAbstract
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Impact Of Currency Translation In Provision Of Impairment On Trade And Other Receivables

No definition available.

Name:	sgbaf_ImpactOfCurrencyTranslationInProvisionOfImpairmentOnTradeAndOtherReceivables
Namespace Prefix:	sgbaf_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Increase In Provision Of Impairment On Trade And Other Receivables

No definition available.

Name:	sgbaf_IncreaseInProvisionOfImpairmentOnTradeAndOtherReceivables
Namespace Prefix:	sgbaf_
Data Type:	xbrli:monetaryItemType
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Period Type:	duration

Other Movement In Provision Of Impairment On Trade And Other Receivables

No definition available.

Name:	sgbaf_OtherMovementInProvisionOfImpairmentOnTradeAndOtherReceivables
Namespace Prefix:	sgbaf_
Data Type:	xbrli:monetaryItemType
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Period Type:	duration

Provision Of Impairment On Trade And Other Receivables

No definition available.

Name:	sgbaf_ProvisionOfImpairmentOnTradeAndOtherReceivables
Namespace Prefix:	sgbaf_
Data Type:	xbrli:monetaryItemType
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Period Type:	instant

Provision of impairment on trade and other receivables in business combination.

No definition available.

Name:	sgbaf_ProvisionOfImpairmentOnTradeAndOtherReceivablesInBusinessCombination
Namespace Prefix:	sgbaf_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Utilised In Provision Of Impairment On Trade And Other Receivables

No definition available.