Inventoried Costs (Details) - USD ($) $ in Millions	Mar. 26, 2017	Dec. 25, 2016
Inventory Disclosure [Abstract]
Raw materials	$ 32.3	$ 31.9
Work in process	30.3	22.1
Finished goods	1.7	1.4
Supplies and other	3.0	1.8
Subtotal inventoried costs	67.3	57.2
Less: Customer advances and progress payments	(2.5)	(1.8)
Total inventoried costs	$ 64.8	$ 55.4