Retirement Plans (Net Pension Cost (Credit)) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Retirement Plans [Abstract]
Service cost plus expected expenses and net of expected plan participant contributions	$ 1,268	$ 1,369	$ 1,214
Interest cost	1,785	1,587	1,590
Expected return on plan assets	(3,001)	(3,275)	(2,940)
Amortization of net actuarial loss	352		18
Net pension cost (credit)	$ 404	$ (319)	$ (118)