Investment Income - Additional Information (Detail) - EUR (€) € in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure of investment income [line items]
Interest income	€ 5,783	€ 6,052	€ 6,479
Fair value interest income	4,811	5,056	5,642
Financial assets impaired [member]
Disclosure of investment income [line items]
Interest income	€ 160	€ 190	€ 230

The amount of income arising from interest.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 8
-IssueDate 2018-01-01
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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