Retirement Benefit Plans, Net Periodic Benefit Cost (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 29, 2019	Jun. 30, 2018	Jun. 29, 2019	Jun. 30, 2018
Pension Benefits [Member]
Components of the net periodic benefit cost [Abstract]
Service cost	$ 263,854	$ 329,901	$ 527,706	$ 659,922
Interest cost	879,080	776,791	1,758,160	1,553,583
Expected return on plan assets	(1,190,331)	(1,304,878)	(2,380,661)	(2,609,758)
Amortization of prior service cost	24,845	32,690	49,690	65,381
Amortization of the net loss	290,550	277,528	581,099	555,056
Net periodic benefit cost	267,998	112,032	535,994	224,184
Additional information [Abstract]
Contributions expected to be made by Company in next fiscal year	600,000		600,000
Employer contributions			0
Postretirement Benefits [Member]
Components of the net periodic benefit cost [Abstract]
Service cost	8,216	9,256	16,432	18,512
Interest cost	20,346	19,291	40,692	38,581
Expected return on plan assets	(14,482)	(13,912)	(28,963)	(27,825)
Amortization of prior service cost	(1,268)	(1,268)	(2,536)	(2,536)
Amortization of the net loss	(20,507)	(16,398)	(41,014)	(32,796)
Net periodic benefit cost	(7,695)	$ (3,031)	(15,389)	$ (6,064)
Additional information [Abstract]
Contributions expected to be made by Company in next fiscal year	$ 105,000		105,000
Employer contributions			$ 33,000