Accumulated Other Comprehensive Income (Loss) (Details 1) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amortization of prior service costs included in cost of product sold	$ 752,715	$ 646,404	$ 950,580
Amortization of prior service costs included in selling, general and administrative expenses (2)	47,482	50,868	48,925
Postretirement medical plan changes	0	47,671	0
Total before tax	36,822	(18,971)	128,720
Post retirement medical plan | Amount Reclassified from Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amortization of prior service costs included in cost of product sold	(6,087)	(4,394)	1,056
Amortization of prior service costs included in selling, general and administrative expenses (2)	(1,197)	(859)	196
Total before tax	(7,283)	(5,253)	1,252
Tax Benefit	2,695	1,944	(463)
Amounts reclassified from AOCI	$ (4,588)	$ (3,309)	$ 789