Retirement Plans (Net Pension Costs) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Retirement Plans [Abstract]
Service cost plus expected expenses and net of expected plan participant contributions	$ 1,369	$ 1,214	$ 1,142
Interest cost	1,587	1,590	1,584
Expected return on plan assets	(3,275)	(2,940)	(2,953)
Amortization of net actuarial loss		18	244
Net pension cost (credit)	$ (319)	$ (118)	$ 17