Pensions and Other Postretirement Benefit Plans (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1,529	$ 1,683
Interest cost	3,895	4,815
Expected return on assets	(4,326)	(4,846)
Amortization of prior service cost/(credit)	24	27
Amortization of net actuarial loss	$ 1,297	1,229
Curtailment gain		(710)
Net periodic benefit cost	$ 2,419	2,198
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	166	157
Interest cost	$ 1,220	$ 1,371
Expected return on assets
Amortization of prior service cost/(credit)	$ (2,244)	$ (2,244)
Amortization of net actuarial loss	$ 1,669	$ 1,454
Curtailment gain
Net periodic benefit cost	$ 811	$ 738