Retirement Agreements and Other Postretirement Benefit Plan Effected of the Funded Status on the Balance Sheet (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Retirement Benefits [Abstract]
Fully eligible active employees	$ (1,089)	$ (956)
Non-eligible active employees	0	0
Plan assets	0	0
Funded status of accumulated postretirement benefit obligation, recognized in other liabilities	$ (1,089)	$ (956)