Pensions and Other Postretirement Benefit Plans (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1,261	$ 1,391
Interest cost	3,578	3,621
Expected return on assets	(4,102)	(4,470)
Curtailment gain		(518)
Amortization of prior service cost/(credit)	34	17
Amortization of net actuarial loss	1,125	1,110
Net periodic benefit cost	1,896	1,151
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	95	116
Interest cost	1,057	1,013
Expected return on assets
Curtailment gain
Amortization of prior service cost/(credit)	(2,244)	(2,244)
Amortization of net actuarial loss	1,114	1,478
Net periodic benefit cost	$ 22	$ 363