Retirement Benefit Plans (Components of Other Comprehensive Income (Loss)) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 25, 2010
Pension and Postretirement Expenses to be Recognized in 2012 [Abstract]
Expected recognition of prior service benefit	$ 0.9
Expected recognition of net acturial loss	5.0
Pension Benefits [Member]
Other Comprehensive Income (Loss) [Abstract]
Transition obligation	0.5	0
Net prior service (cost) benefit	0.4	0.9
Net actuarial gain (loss)	7.2	(7.2)
Other comprehensive income (loss)	8.1	(6.3)
Postretirement Benefits [Member]
Other Comprehensive Income (Loss) [Abstract]
Transition obligation	0	0
Net prior service (cost) benefit	0.7	(0.8)
Net actuarial gain (loss)	2.9	0.9
Other comprehensive income (loss)	$ 3.6	$ 0.1