Pension and Profit Sharing - Benefit Obligation (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Assumptions used to determine benefit obligation:
Discount rate		3.40%	3.50%
Changes in benefit obligation:
Benefit obligation at beginning of year	$ (1,499,798)	$ (1,776,788)	$ (1,904,377)
Interest cost		(55,811)	(59,348)
Service cost	(1,000)	(36,000)	(25,000)
Actuarial gain (loss)	$ (106,000)	99,019	(62,677)
Benefits and plan expenses paid		269,782	274,614
Benefit obligation at end of year		$ (1,499,798)	$ (1,776,788)