Changes in Accumulated Other Comprehensive Income by Component (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Feb. 28, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss)		$ (106,399)	$ (200,828)
Other comprehensive income before reclassifications to consolidated statements of income		(75,597)	86,515
Amounts reclassified from accumulated other comprehensive (loss) income to the consolidated statements of income	$ (19,331)	10,827	7,914
Total other comprehensive (loss) income, net of tax		(64,770)	94,429	$ (57,576)
Accumulated other comprehensive income (loss)		(190,500)	(106,399)	(200,828)
Gains and Losses on Cash Flow Hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss)		72	(227)
Other comprehensive income before reclassifications to consolidated statements of income		(410)	(231)
Amounts reclassified from accumulated other comprehensive (loss) income to the consolidated statements of income	89	1,083	530
Total other comprehensive (loss) income, net of tax		673	299
Accumulated other comprehensive income (loss)		834	72	(227)
Pension and Other Postretirement Benefit Items
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss)		(103,844)	(114,570)
Other comprehensive income before reclassifications to consolidated statements of income		(25,170)	3,342
Amounts reclassified from accumulated other comprehensive (loss) income to the consolidated statements of income	(19,420)	9,744	7,384
Total other comprehensive (loss) income, net of tax		(15,426)	10,726
Accumulated other comprehensive income (loss)		(138,690)	(103,844)	(114,570)
Foreign Currency Items
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss)		(2,627)	(86,031)
Other comprehensive income before reclassifications to consolidated statements of income		(50,017)	83,404
Amounts reclassified from accumulated other comprehensive (loss) income to the consolidated statements of income	$ 0	0	0
Total other comprehensive (loss) income, net of tax		(50,017)	83,404
Accumulated other comprehensive income (loss)		$ (52,644)	$ (2,627)	$ (86,031)