Retirement Benefit Plans (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 27, 2020	Jun. 29, 2019	Jun. 27, 2020	Jun. 29, 2019
Pension Benefits [Member]
Service cost	$ 266,434	$ 263,854	$ 532,870	$ 527,706
Interest cost	714,142	879,080	1,428,285	1,758,160
Expected return on plan assets	1,365,262	1,190,331	2,730,523	2,380,661
Amortization of prior service cost	24,845	24,845	49,690	49,690
Amortization of the net loss	(325,034)	(290,550)	(650,068)	(581,099)
Net periodic benefit cost (benefit)	(34,807)	267,998	(69,610)	535,994
Postretirement Benefits [Member]
Service cost	10,855	8,216	21,710	16,432
Interest cost	11,667	20,346	23,334	40,692
Expected return on plan assets	5,589	14,482	11,178	28,963
Amortization of prior service cost	(2,063)	(1,268)	(4,126)	(2,536)
Amortization of the net loss	(6,377)	20,507	12,754	41,014
Net periodic benefit cost (benefit)	$ 8,493	$ (7,695)	$ 16,986	$ (15,389)