Commitments, contingencies and other (Narrative) (Details) (EUR €) In Thousands, unless otherwise specified	1 Months Ended	0 Months Ended		1 Months Ended	0 Months Ended		1 Months Ended
	Mar. 21, 2011 claim	Jan. 30, 2013 BELGIUM Foreign Tax Authority [Member]	May 20, 2014 BELGIUM Foreign Tax Authority [Member] Two Thousand and Eight [Member]	Jan. 31, 2012 BELGIUM Foreign Tax Authority [Member] Two Thousand and Eight [Member]	Dec. 28, 2012 BELGIUM Foreign Tax Authority [Member] Two Thousand and Five [Member]	Dec. 28, 2012 BELGIUM Foreign Tax Authority [Member] Two Thousand and Nine [Member]	Dec. 31, 2013 BELGIUM Foreign Tax Authority [Member] Two Thousand and Six [Member]	Dec. 31, 2013 BELGIUM Foreign Tax Authority [Member] Two Thousand and Seven [Member]	Dec. 31, 2013 BELGIUM Foreign Tax Authority [Member] Two Thousand and Ten [Member]
Commitments And Contingencies [Line Items]
Number of class action complaints	2
Assessment received from Belgian tax authority (in euros)			€ 30,132	€ 23,789	€ 46,135	€ 35,567	€ 38,817	€ 39,635	€ 43,117
Interest income earned on deposits related to tax assessment		€ 1,583