Commitments, contingencies and other (Narrative) (Details) (BELGIUM, Foreign Tax Authority [Member], EUR €) In Thousands, unless otherwise specified	0 Months Ended	1 Months Ended	0 Months Ended		1 Months Ended
	Jan. 30, 2013	Jan. 31, 2012 Two Thousand and Eight [Member]	Dec. 28, 2012 Two Thousand and Five [Member]	Dec. 28, 2012 Two Thousand and Nine [Member]	Dec. 31, 2013 Two Thousand and Six [Member]	Dec. 31, 2013 Two Thousand and Seven [Member]	Dec. 31, 2013 Two Thousand and Ten [Member]
Commitments And Contingencies [Line Items]
Assessment received from Belgian tax authority (in euros)		€ 23,789	€ 46,135	€ 35,567	€ 38,817	€ 39,635	€ 43,117
Interest Tax Examination, Refund, Interest Income	€ 1,583