Summary of Significant Accounting Policies Update - Information regarding significant accounting policies (Details)	6 Months Ended	12 Months Ended
	Jun. 30, 2018	Dec. 30, 2017
U. S. Government
Revenue Recognition
Revenues From Contracts With U. S. Government, Percentage		24.00%
U. S. Government | Maximum
Revenue Recognition
Percentage of contract price received for performance based payments on US Government Contracts	90.00%
Percentage of costs incurred representing progress payments on US Government Contracts	80.00%
U. S. Government | Fixed-price and fixed-price incentive contracts
Revenue Recognition
Percentage of revenue under fixed-price and fixed-price incentive contracts		80.00%
Commercial Contract | Minimum
Revenue Recognition
Period of warranty programs	1 year
Commercial Contract | Maximum
Revenue Recognition
Period of warranty programs	5 years