Retirement Plans Retirement Plans, Components of Net Pension Cost for the Post Retirement Plan Table (Details) - Postretirement Plan - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Interest Cost	$ 78	$ 104	$ 108
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	(75)	(75)	(75)
Defined Benefit Plan, Amortization of Gain (Loss)	0	(4)	8
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	$ 3	$ 25	$ 41