Significant Customers (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 25, 2016	Dec. 27, 2015
Revenue, Major Customer [Line Items]
Sales to the U.S. Government - amount	$ 751.9	$ 668.7	$ 657.1
U.S. Government | Kratos Government Solutions (KGS)
Revenue, Major Customer [Line Items]
Sales to the U.S. Government - amount	$ 452.8	$ 398.3	$ 402.9
Sales to the U.S. Government - percentage of total revenue	60.00%	60.00%	61.00%