Pensions and Other Postretirement Benefit Plans (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1,319	$ 1,529
Interest cost	4,049	3,895
Expected return on assets	(4,482)	(4,326)
Amortization of prior service cost/(credit)	19	24
Amortization of net actuarial loss	1,164	1,297
Net periodic benefit cost	2,069	2,419
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	127	166
Interest cost	1,221	1,220
Expected return on assets
Amortization of prior service cost/(credit)	(2,244)	(2,244)
Amortization of net actuarial loss	1,410	1,669
Net periodic benefit cost	$ 514	$ 811