Capital and Funding - Summary of Comprehensive Income: Other Comprehensive Income Reconciliation (Detail) - EUR (€) € in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Disclosure of analysis of other comprehensive income by item [Abstract]
Fair value gains/(losses) beginning balance	€ (113)	€ (98)
Cash flow hedges	(68)	6
Available for sale financial assets	(8)	(21)
Fair value gains/(losses) ending balance	(189)	(113)
Defined benefit pension plans beginning balance	(2,453)	(1,473)
Movement during the year	1,282	(980)
Defined benefit pension plans ending balance	(1,171)	(2,453)
Currency retranslation gains/(losses) beginning balance	(3,295)	(3,512)
Other reserves	(903)	189
Retained profit	(27)	17
Non-controlling interest	(53)	11
Currency retranslation gains/(losses) ending balance	€ (4,278)	€ (3,295)

Adjustments for increase (decrease) in employee benefit liabilities to reconcile profit (loss) to net cash flow from (used in) operating activities. [Refer: Profit (loss)]

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The present value, without deducting any plan assets, of expected future payments required to settle the obligation resulting from employee service in the current and prior periods. [Refer: Plan assets, at fair value]

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The fair value of financial instruments designated as hedging instruments. Hedging instruments are designated derivatives or (for a hedge of the risk of changes in foreign currency exchange rates only) designated non-derivative financial assets or non-derivative financial liabilities whose fair value or cash flows are expected to offset changes in the fair value or cash flows of a designated hedged item. [Refer: At fair value [member]; Derivatives [member]; Derivative financial assets; Derivative financial liabilities; Financial instruments, class [member]; Financial assets; Financial liabilities]

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The gains (losses) on available-for-sale financial assets. [Refer: Financial assets available-for-sale]

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The gains (losses) recognised in other comprehensive income on cash flow hedges, net of tax. [Refer: Cash flow hedges [member]]

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The gains (losses) recognised in other comprehensive income on change in value of foreign currency basis spreads, net of tax. [Refer: Other comprehensive income]

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Currency retranslation movement non-controlling interest.

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Currency retranslation movement retained profit.

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Currency retranslation value.

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