Retirement Plans (Income (Loss) Estimated to be Amortized from Accumulated Other Comprehensive Income (Loss) into Net Periodic Cost) (Details) $ in Thousands	Dec. 31, 2018 USD ($)
Amounts that Will be Amortized from Accumulated Other Comprehensive Income (Loss) in Next Twelve Months
Net gain (loss)	$ (302)
Pension Plan
Amounts that Will be Amortized from Accumulated Other Comprehensive Income (Loss) in Next Twelve Months
Net gain (loss)	(444)
Postretirement Plan
Amounts that Will be Amortized from Accumulated Other Comprehensive Income (Loss) in Next Twelve Months
Net gain (loss)	143
SERP
Amounts that Will be Amortized from Accumulated Other Comprehensive Income (Loss) in Next Twelve Months
Net gain (loss)	$ (1)