Retirement Plans, Effect of One-Percentage-Point Change in Assumed Health Care Cost Trend Rate (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Pension Plan [Member]
Effect of one-percentage-point change in assumed health care cost trend rate on postretirement obligation[Abstract]
Effect of one-percentage-point change in assumed health care cost trend rate on postretirement obligation, Increase	$ 0	$ 0
Effect of one-percentage-point change in assumed health care cost trend rate on postretirement obligation, Decrease	0	0
SERP [Member]
Effect of one-percentage-point change in assumed health care cost trend rate on postretirement obligation[Abstract]
Effect of one-percentage-point change in assumed health care cost trend rate on postretirement obligation, Increase	0	0
Effect of one-percentage-point change in assumed health care cost trend rate on postretirement obligation, Decrease	0	0
Other Postretirement Benefits [Member]
Effect of one-percentage-point change in assumed health care cost trend rate on postretirement obligation[Abstract]
Effect of one-percentage-point change in assumed health care cost trend rate on postretirement obligation, Increase	68	75
Effect of one-percentage-point change in assumed health care cost trend rate on postretirement obligation, Decrease	$ (59)	$ (65)