Retirement Benefit Plans, Net Periodic Benefit Cost (Details) - USD ($)	3 Months Ended
	Mar. 30, 2019	Mar. 31, 2018
Pension Benefits [Member]
Components of the net periodic benefit cost [Abstract]
Service cost	$ 263,852	$ 329,960
Interest cost	879,080	776,792
Expected return on plan assets	(1,190,330)	(1,304,880)
Amortization of prior service cost	24,845	32,691
Amortization of the net loss	290,549	277,528
Net periodic benefit cost	267,996	112,091
Additional information [Abstract]
Contributions expected to be made by Company in next fiscal year	600,000
Employer contributions	0
Postretirement Benefits [Member]
Components of the net periodic benefit cost [Abstract]
Service cost	8,216	9,256
Interest cost	20,346	19,290
Expected return on plan assets	(14,481)	(13,913)
Amortization of prior service cost	(1,268)	(1,268)
Amortization of the net loss	(20,507)	(16,398)
Net periodic benefit cost	(7,694)	$ (3,033)
Additional information [Abstract]
Contributions expected to be made by Company in next fiscal year	105,000
Employer contributions	$ 26,000