Commitments and Contingencies (Details) € in Thousands					1 Months Ended	12 Months Ended	36 Months Ended
	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
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