Inventories Long term contracts percentage-of-completion accounting (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 26, 2014	Sep. 27, 2013	Sep. 26, 2014	Sep. 27, 2013
Inventory Disclosure [Abstract]
Decrease to operating income from the quarterly impact of revisions in long term contracts		$ 0.1		$ 2.8
Increase to operating income from the quarterly impact of revisions in long term contracts	$ 1.3		$ 1.5