Inventoried Costs (Details) - USD ($) $ in Millions	Sep. 25, 2016	Dec. 27, 2015
Inventory Disclosure [Abstract]
Raw materials	$ 31.4	$ 32.9
Work in process	27.2	19.2
Finished goods	1.4	2.6
Supplies and other	1.8	1.6
Subtotal inventoried costs	61.8	56.3
Less: Customer advances and progress payments	(3.3)	(0.7)
Total inventoried costs	$ 58.5	$ 55.6