Pension and Other Postretirement Benefit Plans Components of Net Periodic Pension Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Retirement Benefits [Abstract]
Service cost	$ 1,453	$ 1,494	$ 1,456
Interest cost	1,244	1,121	1,329
Expected return on plan assets	(1,077)	(950)	(1,117)
Administrative charges	37	0	0
Curtailment	(1,219)	0	0
Prior service cost	(106)	(77)	(81)
Unrecognized net actuarial loss	1,706	440	593
Net periodic pension cost	$ 2,038	$ 2,028	$ 2,180