Retirement Benefit Plans, Defined Contribution Plan (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 29, 2019	Jun. 30, 2018	Jun. 29, 2019	Jun. 30, 2018
Defined Contribution Plan [Abstract]
Total contributions for the period	$ 229,736	$ 238,070	$ 1,076,568	$ 1,052,566
Regular Matching Contribution [Member]
Defined Contribution Plan [Abstract]
Total contributions for the period	136,796	140,106	293,063	306,121
Transitional Credit Contribution [Member]
Defined Contribution Plan [Abstract]
Total contributions for the period	74,852	81,506	178,376	205,614
Non-discretionary Contribution [Member]
Defined Contribution Plan [Abstract]
Total contributions for the period	$ 18,088	$ 16,458	605,129	$ 540,831
Non-Union U.S. Employees [Member]
Defined Contribution Plan [Abstract]
Total contributions for the period			$ 565,748