Employee Benefit Plans - Schedule of one-percentage-point increase and a one-percentage-point decrease in the assumed health care cost trend rates (Details) - Other Postretirement Benefit Plans, Defined Benefit - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan, Effect of One-Percentage Point Change in Assumed Health Care Cost Trend Rate [Abstract]
Benefit obligation	$ 465,000	$ 399,000
Aggregate of service and interest cost	28,000	26,000
Benefit obligation	(356,000)	(305,000)
Aggregate of service and interest cost	$ (20,000)	$ (19,000)