Commitments and contingencies - Additional Information (Detail) - EUR (€) € in Millions	12 Months Ended
Dec. 31, 2025	Dec. 31, 2024
Commitments and Contingencies [Line Items]
Contractual capital commitments	€ 594	€ 281
Finance Lease Acquired Not Yet Commenced	€ 28
Finance Lease Term Years	4 years
Transponder Service Agreement Expense	€ 205	158
Litigation Claims Amount	0	0
Outstanding Bank Guarantees	29	39
Intelsat Holdings S.à r.l. [Member]
Commitments and Contingencies [Line Items]
Capital Commitments	261
IRIS2 Concession Agreement [Member]
Commitments and Contingencies [Line Items]
Contract Termination Fees	300
Other commitments [Member]
Commitments and Contingencies [Line Items]
Capital Commitments	783	335
Transponder and Teleport Service Commitments	408	47
Cloud Computing Service Commitments	36	59
Optional Additional Commitment	213
Low Earth Orbit Satellite Capacity and Terminal Hardware Commitment	202
Other commitments [Member] \| Top of range [member]
Commitments and Contingencies [Line Items]
Capital Commitments	415
Teleport and Associated Ground Infrastructure [Member]
Commitments and Contingencies [Line Items]
Finance Lease Acquired Not Yet Commenced	€ 9
Finance Lease Term Years	5 years
State of Luxembourg [Member]
Commitments and Contingencies [Line Items]
Capital Commitments	€ 63	64
State of Luxembourg [Member] \| Other commitments [Member]
Commitments and Contingencies [Line Items]
Capital Commitments	€ 63	€ 64

The amount of future capital expenditures that the entity is committed to make.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Note Expiry date 2027-01-01
-Name IAS
-Number 1
-IssueDate 2025-01-01
-Paragraph 112
-Subparagraph c
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=1&code=ifrs-tx-2025-en-b&anchor=para_112_c&doctype=Standard
-URIDate 2025-03-27

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The amount of capital commitments for which the entity has entered into a contract. [Refer: Capital commitments]

+ References

+ Details

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

- Definition

Cloud computing service commitments.

+ References

No definition available.

+ Details

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- References

No definition available.

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- Definition

Finance lease acquired not yet commenced.

+ References

No definition available.

+ Details

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- Definition

Finance lease term years.

+ References

No definition available.

+ Details

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- Definition

Litigation claims amount.

+ References

No definition available.

+ Details

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Balance Type:	debit
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- Definition

Low earth orbit satellite capacity and terminal hardware commitment.

+ References

No definition available.

+ Details

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

- Definition

Optional additional commitment.

+ References

No definition available.

+ Details

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

- Definition

Outstanding bank guarantees.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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- Definition

Pre financing received from government or commission.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
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- Definition

Transponder and teleport service commitments.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Transponder service agreement expense.

+ References

No definition available.

+ Details

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Namespace Prefix:	sgbaf_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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- Details

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- Details

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