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Pensions and Other Post-employment Benefit Obligations - Additional Information (Detail) - EUR (€) € in Millions | 3 Months Ended | 12 Months Ended
--- | --- | ---
Sep. 30, 2018 | Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Disclosure of defined benefit plans [line items] |  |  |  |
Gain from negative past service cost | € 36 |  |  |
Weighted-average maturity of defined benefit obligations |  |  | 13 years 3 months 18 days | 14 years
Pensions [member] |  |  |  |
Disclosure of defined benefit plans [line items] |  |  |  |
Expected contributions to pension and other benefits |  | € 26 |  |
Other benefits [member] |  |  |  |
Disclosure of defined benefit plans [line items] |  |  |  |
Expected contributions to pension and other benefits |  | € 19 |  |
Actuarial assumption of discount rates [member] |  |  |  |
Disclosure of defined benefit plans [line items] |  |  |  |
Increase in actuarial assumption |  |  | 0.50% |
Decrease in actuarial assumption |  |  | 0.50% |

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- Definition Weighted-average maturity of defined benefit obligations. + References No definition available. + Details
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- Definition Line items represent concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes of the table. + References No definition available. + Details
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- Definition The estimate of the expected contributions to be made to a defined benefit plan for the next annual reporting period. [Refer: Defined benefit plans [member]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 19 -IssueDate 2018-01-01 -Paragraph 147 -Subparagraph b -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2018-03-01&anchor=para_147_b&doctype=Standard -URIDate 2018-03-16 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 19 -IssueDate 2018-01-01 -Paragraph 148 -Subparagraph d -Clause iii -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2018-03-01&anchor=para_148_d_iii&doctype=Standard -URIDate 2018-03-16 + Details
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- Definition The reasonably possible percentage of the decrease in the actuarial assumption used to determine the present value of defined benefit obligation. [Refer: Actuarial assumptions [member]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 19 -IssueDate 2018-01-01 -Paragraph 145 -Subparagraph a -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2018-03-01&anchor=para_145_a&doctype=Standard -URIDate 2018-03-16 + Details
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- Definition The reasonably possible percentage of the increase in the actuarial assumption used to determine the present value of defined benefit obligation. [Refer: Actuarial assumptions [member]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 19 -IssueDate 2018-01-01 -Paragraph 145 -Subparagraph a -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2018-03-01&anchor=para_145_a&doctype=Standard -URIDate 2018-03-16 + Details
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