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Investments Accounted for Under Equity Method - Additional Information (Detail) - EUR (€) € in Millions | 3 Months Ended | 6 Months Ended | 12 Months Ended
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Jun. 30, 2018 | Jun. 30, 2017 | Jun. 30, 2018 | Jun. 30, 2017 | Dec. 31, 2017
Share of profit (loss) of associates and joint ventures accounted for using equity method [abstract] |  |  |  |  |
Cumulative share of losses of joint-ventures in excess of initial investment |  |  | € 28 |  |
Share of losses of joint-ventures in excess of initial investment | € 9 | € 7 | € 12 | € 13 | € 29

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- Definition Cumulative share of profit (loss) of joint ventures accounted for using equity method. + References No definition available. + Details
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- References No definition available. + Details
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- Definition The entity's share of the profit (loss) of joint ventures accounted for using the equity method. [Refer: Investments accounted for using equity method; Joint ventures [member]; Profit (loss)] + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IAS -Number 1 -IssueDate 2017-01-01 -Paragraph 85 -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2017-03-01&anchor=para_85&doctype=Standard -URIDate 2017-03-09 + Details
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