Income Tax - Summary of Income Tax Reconciliation Using Composite Statutory Income Tax Rate Applicable by Tax Jurisdictions (Detail) - EUR (€) € in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure Of Income Tax Expense [Abstract]
Income / (Loss) before income tax	€ 49	€ 65	€ (584)
Composite statutory income tax rate applicable by tax jurisdiction	31.90%	24.90%	38.20%
Income tax (expense) / benefit calculated at composite statutory tax rate applicable by tax jurisdictions	€ (16)	€ (16)	€ 223
Tax effect of:
Changes in recognized and unrecognized deferred tax assets	(61)	(45)	(177)
Change in tax rate	(11)	(6)
Other	8	(2)	(14)
Income tax (expense) / benefit	€ (80)	€ (69)	€ 32
Effective income tax rate	163.00%	106.00%	5.00%

Disclosure of income tax expense.

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Adjustments for deferred tax expense to reconcile profit (loss) to net cash flow from (used in) operating activities. [Refer: Deferred tax expense (income); Profit (loss)]

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The applicable income tax rate.

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The tax expense (income) divided by the accounting profit. [Refer: Accounting profit]

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The aggregate amount included in the determination of profit (loss) for the period in respect of current tax and deferred tax that relate to continuing operations. [Refer: Continuing operations [member]; Current tax expense (income); Deferred tax expense (income)]

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The amount that represents the difference between the tax expense (income) and the product of the accounting profit multiplied by the applicable tax rate(s) that the entity does not separately disclose in the same statement or note. [Refer: Accounting profit; Applicable tax rate]

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The profit (loss) from continuing operations before tax expense or income. [Refer: Profit (loss)]

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The amount that represents the difference between the tax expense (income) and the product of the accounting profit multiplied by the applicable tax rate(s) that relates to changes in the tax rate. [Refer: Accounting profit]

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The product of the accounting profit multiplied by the applicable tax rate(s). [Refer: Accounting profit; Applicable tax rate]

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