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Operating Segment Information - Summary of Segment Assets (Detail) - EUR (€) € in Millions | Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014
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Disclosure of segment assets [line items] |  |  |  |
Total Assets | € 3,711 | € 3,787 |  |
Deferred income tax assets | 164 | 252 |  |
Cash and cash equivalents | 269 | 347 | € 472 | € 991
Other financial assets | 179 | 166 |  |
Segment [member] |  |  |  |
Disclosure of segment assets [line items] |  |  |  |
Total Assets | 3,099 | 3,022 |  |
Segment [member] | P&ARP [member] |  |  |  |
Disclosure of segment assets [line items] |  |  |  |
Total Assets | 1,629 | 1,652 |  |
Segment [member] | A&T [member] |  |  |  |
Disclosure of segment assets [line items] |  |  |  |
Total Assets | 769 | 768 |  |
Segment [member] | AS&I [member] |  |  |  |
Disclosure of segment assets [line items] |  |  |  |
Total Assets | 449 | 390 |  |
Segment [member] | Holdings & Corporate [member] |  |  |  |
Disclosure of segment assets [line items] |  |  |  |
Total Assets | 252 | 212 |  |
Unallocated amounts [member] |  |  |  |
Disclosure of segment assets [line items] |  |  |  |
Deferred income tax assets | 164 | 252 |  |
Cash and cash equivalents | 269 | 347 |  |
Other financial assets | € 179 | € 166 |  |

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- Definition The amount of cash on hand and demand deposits, along with short-term, highly liquid investments that are readily convertible to known amounts of cash and that are subject to an insignificant risk of changes in value. [Refer: Cash; Cash equivalents] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 7 -IssueDate 2017-01-01 -Paragraph 45 -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=7&date=2017-03-01&anchor=para_45&doctype=Standard -URIDate 2017-03-09 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 12 -IssueDate 2017-01-01 -Paragraph B13 -Subparagraph a -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=12&date=2017-03-01&anchor=para_B13_a&doctype=Appendix&seq=2 -URIDate 2017-03-09 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 1 -IssueDate 2017-01-01 -Paragraph 54 -Subparagraph i -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2017-03-01&anchor=para_54_i&doctype=Standard -URIDate 2017-03-09 + Details
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