Accumulated Other Comprehensive Income (Reclassifications) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Revenue	$ 832,856	$ 733,273	$ 2,575,240	$ 2,206,866
Interest expense, net	(25,483)	(28,601)	(85,959)	(81,877)
Pension and Postretirement Benefit Plans	(269,387)	(288,093)	(847,281)	(861,738)
Income from continuing operations before taxes	45,129	56,265	159,882	183,022
Benefit (provision) from income taxes	1,976	(10,828)	(20,745)	(38,700)
Net income	76,953	57,358	178,680	171,392
Reclassification out of Accumulated Other Comprehensive Loss | Cash flow hedges
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Revenue	(38)	(139)	38	(133)
Cost of sales	52	(59)	(33)	89
Interest expense, net	(825)	(507)	(1,839)	(1,521)
Income from continuing operations before taxes	(811)	(705)	(1,834)	(1,565)
Benefit (provision) from income taxes	206	274	468	610
Net income	(605)	(431)	(1,366)	(955)
Reclassification out of Accumulated Other Comprehensive Loss | Available for sale securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest expense, net	(40)	(298)	150	(524)
Benefit (provision) from income taxes	10	110	(38)	194
Net income	(30)	(188)	112	(330)
Reclassification out of Accumulated Other Comprehensive Loss | Pension and postretirement benefit plans
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income from continuing operations before taxes	(11,208)	(10,228)	(32,616)	(30,518)
Benefit (provision) from income taxes	2,399	3,484	7,766	10,440
Net income	(8,809)	(6,744)	(24,850)	(20,078)
Reclassification out of Accumulated Other Comprehensive Loss | Transition credit
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Pension and Postretirement Benefit Plans	2	2	5	6
Reclassification out of Accumulated Other Comprehensive Loss | Prior service costs
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Pension and Postretirement Benefit Plans	(79)	(41)	(188)	(125)
Reclassification out of Accumulated Other Comprehensive Loss | Actuarial losses
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Pension and Postretirement Benefit Plans	(9,996)	(10,189)	(31,298)	(30,399)
Reclassification out of Accumulated Other Comprehensive Loss | Settlements
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Pension and Postretirement Benefit Plans	$ (1,135)	$ 0	$ (1,135)	$ 0