Retirement Benefit Plans (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jul. 03, 2021	Jun. 27, 2020	Jul. 03, 2021	Jun. 27, 2020
Pension Benefit [Member]
Service cost	$ 271,835	$ 266,434	$ 543,668	$ 532,870
Interest cost	504,254	714,142	1,008,509	1,428,285
Expected return on plan assets	(1,448,675)	(1,365,262)	(2,897,349)	(2,730,523)
Amortization of prior service cost	24,845	24,845	49,690	49,690
Amortization of the net loss	432,536	325,034	865,075	650,068
Net periodic benefit cost	215,205	(34,807)	(430,407)	(69,610)
Other Postretirement Benefit [Member]
Service cost	13,626	10,855	27,252	21,710
Interest cost	9,842	11,667	19,684	23,334
Expected return on plan assets	(6,420)	(5,589)	(12,840)	(11,178)
Amortization of prior service cost	0	2,063	0	(4,126)
Amortization of the net loss	(3,094)	(6,377)	(6,188)	(12,754)
Net periodic benefit cost	(13,954)	(8,493)	(27,908)	(16,986)
Gain on significant event	$ 0	$ 0	$ 0	$ 0