Inventoried Costs (Details) - USD ($) $ in Millions	Oct. 01, 2017	Dec. 25, 2016
Inventory Disclosure [Abstract]
Raw materials	$ 33.0	$ 31.9
Work in process	26.9	22.1
Finished goods	2.2	1.4
Supplies and other	2.0	1.8
Subtotal inventoried costs	64.1	57.2
Less: Customer advances and progress payments	(1.3)	(1.8)
Total inventoried costs	$ 62.8	$ 55.4