Significant Customers (Details) - U.S. Government - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 28, 2015	Jun. 29, 2014	Jun. 28, 2015	Jun. 29, 2014
Revenue, Major Customer [Line Items]
Sales to the U.S. Government - amount	$ 99.2	$ 105.3	$ 194.2	$ 204.1
Government contracts | Revenue
Revenue, Major Customer [Line Items]
Sales to the U.S. Government - percentage of total revenue	62.00%	52.00%	61.00%	54.00%