Savings Plans, Pension Plans and Other Postretirement Employee Benefits (Amounts Recognized in AOCI on Consolidated Balance Sheet) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Net amount recognized	$ (110,744)	$ (114,503)
Pension Plans [Member]
Net loss	120,006	127,307
Prior service cost (credit)	621	937
Net amount recognized	120,627	128,244	$ 134,261	$ 117,167
Other Postretirement Employee Benefits [Member]
Net loss	8,778	9,634
Prior service cost (credit)	(17,960)	(23,375)
Net amount recognized	$ (9,182)	$ (13,741)	$ (15,869)	$ (18,447)