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Deferred Income Taxes - Additional Information (Detail) - EUR (€)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Significant components of deferred tax assets and liabilities [line items]
US tax rate decrease impact in P&L		€ (16,000,000)
US tax rate decrease impact in OCI		(8,000,000)
Unused tax losses for which no deferred tax asset recognized	€ 1,257,000,000	1,393,000,000
Related tax impact	321,000,000	€ 356,000,000
Switzerland [member]
Significant components of deferred tax assets and liabilities [line items]
Tax loss carried forwards	€ 0

X

- Definition

Increase (decrease) in deferred tax recognised in profit or loss due to change in rate.

+ References

No definition available.

+ Details

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X

- Definition

Non recognized tax assets.

+ References

No definition available.

+ Details

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X

- Definition

Significant components of deferred tax assets and liabilities line items.

+ References

No definition available.

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- Definition

Unused tax losses carried forward.

+ References

No definition available.

+ Details

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X

- Definition

The increase (decrease) in accumulated deferred tax recognised in other comprehensive income due to change in the tax rate. [Refer: Other comprehensive income]

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 1
-IssueDate 2018-01-01
-Paragraph 85
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2018-03-01&anchor=para_85&doctype=Standard
-URIDate 2018-03-16

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X

- Definition

The amount of unused tax losses for which no deferred tax asset is recognised in the statement of financial position. [Refer: Unused tax losses [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 12
-IssueDate 2018-01-01
-Paragraph 81
-Subparagraph e
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=12&date=2018-03-01&anchor=para_81_e&doctype=Standard
-URIDate 2018-03-16

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