Shareholders' equity - Perpetual subordinated notes (Details) € in Millions	Apr. 30, 2019 EUR (€)
Perpetual subordinated notes issued, 1.750%, callable in 2024
Shareholders' equity
Interest rate (as percent)	1.75%
Principal amount	€ 1,500
Perpetual subordinated notes tendered, 2.250%, callable in 2021
Shareholders' equity
Interest rate (as percent)	2.25%
Principal amount	€ 1,500

The nominal or face amount of a financial instrument, used to calculate payments made on that instrument.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 1
-IssueDate 2018-01-01
-Paragraph 112
-Subparagraph c
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2018-03-01&anchor=para_112_c&doctype=Standard
-URIDate 2018-03-16

Name:	ifrs-full_NotionalAmount
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant