INTANGIBLE ASSETS AND GOODWILL - Changes in Intangible Assets and Goodwill (Details) € in Millions	6 Months Ended
Jun. 30, 2024 EUR (€)
Changes in intangible assets other than goodwill [abstract]
Intangible assets (excluding goodwill), beginning balance	€ 47
Additions	1
Amortization expense	(4)
Effect of changes in foreign exchange rates	1
Intangible assets (excluding goodwill), ending balance	45
Changes in goodwill [abstract]
Goodwill, beginning balance	462
Effect of changes in foreign exchange rates	15
Goodwill, ending balance	477
Acquired through business combination	0
Cost
Changes in intangible assets other than goodwill [abstract]
Intangible assets (excluding goodwill), ending balance	230
Changes in goodwill [abstract]
Goodwill, ending balance	477
Less accumulated depreciation and impairment
Changes in intangible assets other than goodwill [abstract]
Intangible assets (excluding goodwill), ending balance	(185)
Changes in goodwill [abstract]
Goodwill, ending balance	0
Technology
Changes in intangible assets other than goodwill [abstract]
Intangible assets (excluding goodwill), beginning balance	16
Additions	0
Amortization expense	(1)
Effect of changes in foreign exchange rates	1
Intangible assets (excluding goodwill), ending balance	16
Technology \| Cost
Changes in intangible assets other than goodwill [abstract]
Intangible assets (excluding goodwill), ending balance	92
Technology \| Less accumulated depreciation and impairment
Changes in intangible assets other than goodwill [abstract]
Intangible assets (excluding goodwill), ending balance	(76)
Computer Software
Changes in intangible assets other than goodwill [abstract]
Intangible assets (excluding goodwill), beginning balance	13
Additions	0
Amortization expense	(2)
Effect of changes in foreign exchange rates	0
Intangible assets (excluding goodwill), ending balance	11
Computer Software \| Cost
Changes in intangible assets other than goodwill [abstract]
Intangible assets (excluding goodwill), ending balance	88
Computer Software \| Less accumulated depreciation and impairment
Changes in intangible assets other than goodwill [abstract]
Intangible assets (excluding goodwill), ending balance	(77)
Customer relationships
Changes in intangible assets other than goodwill [abstract]
Intangible assets (excluding goodwill), beginning balance	12
Additions	0
Amortization expense	0
Effect of changes in foreign exchange rates	0
Intangible assets (excluding goodwill), ending balance	12
Customer relationships \| Cost
Changes in intangible assets other than goodwill [abstract]
Intangible assets (excluding goodwill), ending balance	42
Customer relationships \| Less accumulated depreciation and impairment
Changes in intangible assets other than goodwill [abstract]
Intangible assets (excluding goodwill), ending balance	(30)
Work in Progress
Changes in intangible assets other than goodwill [abstract]
Intangible assets (excluding goodwill), beginning balance	3
Additions	1
Amortization expense	(1)
Effect of changes in foreign exchange rates	0
Intangible assets (excluding goodwill), ending balance	3
Work in Progress \| Cost
Changes in intangible assets other than goodwill [abstract]
Intangible assets (excluding goodwill), ending balance	4
Work in Progress \| Less accumulated depreciation and impairment
Changes in intangible assets other than goodwill [abstract]
Intangible assets (excluding goodwill), ending balance	(1)
Other
Changes in intangible assets other than goodwill [abstract]
Intangible assets (excluding goodwill), beginning balance	3
Additions	0
Amortization expense	0
Effect of changes in foreign exchange rates	0
Intangible assets (excluding goodwill), ending balance	3
Other \| Cost
Changes in intangible assets other than goodwill [abstract]
Intangible assets (excluding goodwill), ending balance	4
Other \| Less accumulated depreciation and impairment
Changes in intangible assets other than goodwill [abstract]
Intangible assets (excluding goodwill), ending balance	€ (1)

The amount of additional goodwill recognised, except goodwill included in a disposal group that, on acquisition, meets the criteria to be classified as held for sale in accordance with IFRS 5. [Refer: Goodwill; Disposal groups classified as held for sale [member]]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition

The amount of additions to intangible assets other than goodwill, other than those acquired through business combinations. [Refer: Business combinations [member]; Intangible assets other than goodwill]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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The amount of amortisation of intangible assets other than goodwill. [Refer: Depreciation and amortisation expense; Intangible assets other than goodwill]

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The amount of assets representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognised. [Refer: Business combinations [member]]

+ References

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The increase (decrease) in goodwill resulting from net exchange differences arising on the translation of the financial statements from the functional currency into a different presentation currency, including the translation of a foreign operation into the presentation currency of the reporting entity. [Refer: Goodwill]

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The increase (decrease) in intangible assets other than goodwill resulting from net exchange differences arising on the translation of the financial statements from the functional currency into a different presentation currency, including the translation of a foreign operation into the presentation currency of the reporting entity. [Refer: Intangible assets other than goodwill]

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- Definition

The amount of identifiable non-monetary assets without physical substance. This amount does not include goodwill. [Refer: Goodwill]

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