INTANGIBLE ASSETS AND GOODWILL - Changes in Intangible Assets and Goodwill (Details) € in Millions	6 Months Ended
Jun. 30, 2021 EUR (€)
Changes in intangible assets other than goodwill [abstract]
Intangible assets (excluding goodwill), beginning balance	€ 61
Additions	2
Amortization expense	(5)
Transfer	0
Effect of changes in foreign exchange rates	1
Intangible assets (excluding goodwill), ending balance	59
Changes in goodwill [abstract]
Goodwill, beginning balance	417
Effect of changes in foreign exchange rates	13
Goodwill, ending balance	430
Cost
Changes in intangible assets other than goodwill [abstract]
Intangible assets (excluding goodwill), ending balance	214
Changes in goodwill [abstract]
Goodwill, ending balance	430
Less accumulated depreciation and impairment
Changes in intangible assets other than goodwill [abstract]
Intangible assets (excluding goodwill), ending balance	(155)
Technology
Changes in intangible assets other than goodwill [abstract]
Intangible assets (excluding goodwill), beginning balance	18
Additions	0
Amortization expense	(1)
Transfer	0
Effect of changes in foreign exchange rates	1
Intangible assets (excluding goodwill), ending balance	18
Technology \| Cost
Changes in intangible assets other than goodwill [abstract]
Intangible assets (excluding goodwill), ending balance	82
Technology \| Less accumulated depreciation and impairment
Changes in intangible assets other than goodwill [abstract]
Intangible assets (excluding goodwill), ending balance	(64)
Computer Software
Changes in intangible assets other than goodwill [abstract]
Intangible assets (excluding goodwill), beginning balance	15
Additions	0
Amortization expense	(4)
Transfer	4
Effect of changes in foreign exchange rates	0
Intangible assets (excluding goodwill), ending balance	15
Computer Software \| Cost
Changes in intangible assets other than goodwill [abstract]
Intangible assets (excluding goodwill), ending balance	80
Computer Software \| Less accumulated depreciation and impairment
Changes in intangible assets other than goodwill [abstract]
Intangible assets (excluding goodwill), ending balance	(65)
Customer relationships
Changes in intangible assets other than goodwill [abstract]
Intangible assets (excluding goodwill), beginning balance	13
Additions	0
Amortization expense	0
Transfer	0
Effect of changes in foreign exchange rates	0
Intangible assets (excluding goodwill), ending balance	13
Customer relationships \| Cost
Changes in intangible assets other than goodwill [abstract]
Intangible assets (excluding goodwill), ending balance	38
Customer relationships \| Less accumulated depreciation and impairment
Changes in intangible assets other than goodwill [abstract]
Intangible assets (excluding goodwill), ending balance	(25)
Work in Progress
Changes in intangible assets other than goodwill [abstract]
Intangible assets (excluding goodwill), beginning balance	13
Additions	2
Amortization expense	0
Transfer	(4)
Effect of changes in foreign exchange rates	0
Intangible assets (excluding goodwill), ending balance	11
Work in Progress \| Cost
Changes in intangible assets other than goodwill [abstract]
Intangible assets (excluding goodwill), ending balance	12
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	2
Additions	0
Amortization expense	0
Transfer	0
Effect of changes in foreign exchange rates	0
Intangible assets (excluding goodwill), ending balance	2
Other \| Cost
Changes in intangible assets other than goodwill [abstract]
Intangible assets (excluding goodwill), ending balance	2
Other \| Less accumulated depreciation and impairment
Changes in intangible assets other than goodwill [abstract]
Intangible assets (excluding goodwill), ending balance	€ 0

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]

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

The amount of amortisation of intangible assets other than goodwill. [Refer: Depreciation and amortisation expense; Intangible assets other than goodwill]

+ References

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

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

+ References

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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]

+ References

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- Definition

The increase (decrease) in intangible assets and goodwill resulting from transfers. [Refer: Intangible assets and goodwill]

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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- Definition

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

+ References

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