Pension Plan (Details) - Change in unrecognized pension costs recorded in other comprehensive loss - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Pension Plan (Details) - Change in unrecognized pension costs recorded in other comprehensive loss [Line Items]
Balance at beginning of year	$ 7,954,000	$ 7,301,000
Net actuarial loss	606,000	882,000
Recognized loss	(264,000)	(229,000)
Balance at end of year	$ 8,296,000	$ 7,954,000