Pension Plans - SERP (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
SERP
Defined contribution plan
Expenses recorded	$ 25,000	$ 30,000	$ 75,000	$ 90,000
Employer contributions	0	0	88,000	120,000
Liability for pension benefits	75,000		75,000		$ 90,000
Defined Contribution 401 K Plan
Defined contribution plan
Employer contributions	$ 34,000	$ 28,000	$ 112,000	$ 93,000