Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement of Comprehensive Income [Abstract]
Tax expense recognized on the amortization of prior service cost	$ (18,000)	$ (20,148)	$ (22,000)
Tax expense recognized on the net gain (loss)	(41,000)	368,387	(49,000)
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Tax	1,392,000	$ (176,000)	$ (555,000)
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Interest Rate Swaps During Period, Tax	$ (12,000)