Changes in Accumulated Other Comprehensive Income by Component (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance	$ 1,270,528	$ 1,203,056	$ 1,260,321
Other comprehensive income before reclassifications to consolidated statements of income	75,547	(27,868)
Amounts reclassified from accumulated other comprehensive (loss) income to the consolidated statements of income	12,633	7,873
Total other comprehensive (loss) income, net of tax	88,180	(19,995)	(64,770)
Balance	1,382,677	1,270,528	1,203,056
Gains and Losses on Cash Flow Hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance	(115)	834
Other comprehensive income before reclassifications to consolidated statements of income	(1,674)	(1,436)
Amounts reclassified from accumulated other comprehensive (loss) income to the consolidated statements of income	1,032	487
Total other comprehensive (loss) income, net of tax	(642)	(949)
Balance	(757)	(115)	834
Pension and Other Postretirement Benefit Items
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance	(144,047)	(138,690)
Other comprehensive income before reclassifications to consolidated statements of income	(9,673)	(12,743)
Amounts reclassified from accumulated other comprehensive (loss) income to the consolidated statements of income	11,601	7,386
Total other comprehensive (loss) income, net of tax	1,928	(5,357)
Balance	(142,119)	(144,047)	(138,690)
Foreign Currency Items
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance	(66,333)	(52,644)
Other comprehensive income before reclassifications to consolidated statements of income	86,894	(13,689)
Amounts reclassified from accumulated other comprehensive (loss) income to the consolidated statements of income	0	0
Total other comprehensive (loss) income, net of tax	86,894	(13,689)
Balance	20,561	(66,333)	(52,644)
Accumulated Other Non-Owner Changes to Equity
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance	(210,495)	(190,500)	(106,399)
Balance	$ (122,315)	$ (210,495)	$ (190,500)

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount after tax, before reclassification adjustments of other comprehensive income (loss).

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Amount after tax and reclassification adjustments of other comprehensive income (loss).

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