Pensions and Other Postretirement Benefit Plans (Schedule of Net Periodic Benefit Plan Cost) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Pension Plans [Member]
Components of net periodic benefit cost:
Service cost	$ 650	$ 790
Interest cost	1,994	2,013
Expected return on assets	(2,207)	(2,235)
Amortization of prior service cost/(credit)	9	13
Amortization of net actuarial loss	573	670
Net periodic benefit cost	1,019	1,251
Other Postretirement Benefits [Member]
Components of net periodic benefit cost:
Service cost	63	83
Interest cost	$ 611	$ 610
Expected return on assets
Amortization of prior service cost/(credit)	$ (1,122)	$ (1,122)
Amortization of net actuarial loss	705	835
Net periodic benefit cost	$ 257	$ 406