Retirement Benefit Plans, Defined Contribution Plan (Details) - USD ($)	3 Months Ended
	Mar. 30, 2019	Mar. 31, 2018
Defined Contribution Plan [Abstract]
Total contributions made for the period	$ 846,832	$ 814,496
Regular Matching Contribution [Member]
Defined Contribution Plan [Abstract]
Total contributions made for the period	156,267	166,015
Transitional Credit Contribution [Member]
Defined Contribution Plan [Abstract]
Total contributions made for the period	103,524	124,108
Non-discretionary Contribution [Member]
Defined Contribution Plan [Abstract]
Total contributions made for the period	587,041	$ 524,373
Non-Union U.S. Employees [Member]
Defined Contribution Plan [Abstract]
Total contributions made for the period	$ 565,748