Facility consolidation and asset impairment charges (Details Textual) (Publishing [Member], USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 29, 2013	Sep. 23, 2012	Sep. 29, 2013	Sep. 23, 2012
Property Plant And Equipment [Member]
Facility consolidation and asset impairment charges (Textual) [Abstract]
Asset impairment and other charges, pre-tax amount	$ 5.9	$ 4.2	$ 15.2	$ 14.1
Asset impairment and other charges, after-tax amount	3.6	2.4	9.2	8.4
Asset impairment and other charges, per share amount (In USD per share)	$ 0.02	$ 0.01	$ 0.04	$ 0.04
Publishing Assets Donated [Member]
Facility consolidation and asset impairment charges (Textual) [Abstract]
Asset impairment and other charges, pre-tax amount			0.9
Asset impairment and other charges, after-tax amount			$ 0.6
Asset impairment and other charges, per share amount (In USD per share)			$ 0.01