Facility consolidation and asset impairment charges (Details Textual) (Publishing [Member], USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 24, 2012	Jun. 30, 2013	Jun. 24, 2012
Property Plant And Equipment [Member]
Facility consolidation and asset impairment charges (Textual) [Abstract]
Asset impairment and other charges, pre-tax amount	$ 4.5	$ 5.1	$ 9.3	$ 9.9
Asset impairment and other charges, after-tax amount	2.7	3.1	5.6	6.0
Asset impairment and other charges, per share amount (In USD per share)	$ 0.01	$ 0.01	$ 0.02	$ 0.03
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