Pension Plans - SERP (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
SERP
Defined contribution plan
Expenses recorded	$ 30,000	$ 90,000	$ 27,000	$ 81,000
Employer contributions	0	120,000	0	108,000
Liability for pension benefits	90,000		90,000		$ 120,000
401(k) plan
Defined contribution plan
Employer contributions	$ 28,000	$ 93,000	$ 31,000	$ 90,000