Commitments and Contingencies (Details) € in Thousands						1 Months Ended	12 Months Ended	36 Months Ended
	Oct. 05, 2021 complaint	Apr. 23, 2021 complaint	Dec. 22, 2020 EUR (€)	Oct. 22, 2020 EUR (€)	Mar. 10, 2020 EUR (€)	Jun. 30, 2021 EUR (€)	Dec. 31, 2016 EUR (€)	Dec. 31, 2014 EUR (€)
Georgia State Court Investor Actions
Commitments And Contingencies [Line Items]
Number of complaints | complaint		4
Georgia State Court Investor Actions | Pending Litigation | Subsequent Event
Commitments And Contingencies [Line Items]
Number of complaints | complaint	4
Belgium | Foreign tax authority | 2005
Commitments And Contingencies [Line Items]
Assessment received from Belgian tax authority (in euros)								€ 46,135
Belgium | Foreign tax authority | 2006
Commitments And Contingencies [Line Items]
Assessment received from Belgian tax authority (in euros)								38,817
Belgium | Foreign tax authority | 2007
Commitments And Contingencies [Line Items]
Assessment received from Belgian tax authority (in euros)								39,635
Belgium | Foreign tax authority | 2008
Commitments And Contingencies [Line Items]
Assessment received from Belgian tax authority (in euros)								30,131
Belgium | Foreign tax authority | 2009
Commitments And Contingencies [Line Items]
Assessment received from Belgian tax authority (in euros)								25,486
Belgium | Foreign tax authority | 2010
Commitments And Contingencies [Line Items]
Assessment received from Belgian tax authority (in euros)								€ 43,117
Belgium | Foreign tax authority | 2016
Commitments And Contingencies [Line Items]
Assessment received from Belgian tax authority (in euros)					€ 67,959		€ 67,959
Belgium | Foreign tax authority | 2017
Commitments And Contingencies [Line Items]
Assessment received from Belgian tax authority (in euros)			€ 17,655
LUXEMBOURG | Foreign tax authority | 2016
Commitments And Contingencies [Line Items]
Assessment received from Belgian tax authority (in euros)						€ 81,651
LUXEMBOURG | Foreign tax authority | 2017
Commitments And Contingencies [Line Items]
Assessment received from Belgian tax authority (in euros)				€ 65,152
LUXEMBOURG | Foreign tax authority | 2013
Commitments And Contingencies [Line Items]
Assessment received from Belgian tax authority (in euros)				€ 45,466
LUXEMBOURG | Foreign tax authority | 2014
Commitments And Contingencies [Line Items]
Assessment received from Belgian tax authority (in euros)						57,545
LUXEMBOURG | Foreign tax authority | 2015
Commitments And Contingencies [Line Items]
Assessment received from Belgian tax authority (in euros)						72,704
LUXEMBOURG | Foreign tax authority | 2018
Commitments And Contingencies [Line Items]
Assessment received from Belgian tax authority (in euros)						€ 49,178