Retirement Agreements and Other Postretirement Benefit Plan Development of the Accumulated Postretirement Benefit Obligation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Accrued postretirement benefit obligation at beginning of year	$ (882)	$ (896)
Service cost – benefits earned during the year	0	0	$ 0
Interest cost on projected benefit obligation	(33)	(32)	(37)
Actuarial (loss) gain	(41)	46
Accrued postretirement benefit obligation at end of year	$ (956)	$ (882)	$ (896)