Pensions and Other Postretirement Benefit Plans (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 2,268	$ 2,521
Interest cost	5,779	7,217
Expected return on assets	(6,418)	(7,260)
Amortization of prior service cost/(credit)	36	41
Amortization of net actuarial loss	$ 1,924	1,845
Curtailment gain		(710)
Net periodic benefit cost	$ 3,589	3,654
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	250	236
Interest cost	$ 1,831	$ 2,057
Expected return on assets
Amortization of prior service cost/(credit)	$ (3,366)	$ (3,366)
Amortization of net actuarial loss	$ 2,504	$ 2,181
Curtailment gain
Net periodic benefit cost	$ 1,219	$ 1,108