Pension and Postretirement Plans (Consolidated Balance Sheet) (Details 2) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Noncurrent asset	$ 881,593	$ 979,970
Current liability	0	0
Noncurrent liability	0	0
Recognized asset (liability)	881,593	979,970
Supplemental Executive Retirement Plan (SERP) [Member]
Defined Benefit Plan Disclosure [Line Items]
Noncurrent asset	0	0
Current liability	(5,580)	(5,442)
Noncurrent liability	(100,946)	(99,562)
Recognized asset (liability)	(106,526)	(105,004)
Other Postretirement Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Current liability	(2,312)	(3,444)
Noncurrent liability	(21,859)	(33,947)
Recognized asset (liability)	$ (24,171)	$ (37,391)