Accumulated Other Comprehensive Loss (Reclassification) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Other income (expense), net	$ 3,513	$ (592)	$ (994)
Income tax (expense) benefit	(18,544)	(7,807)	(22,938)
Net income	49,990	47,319	$ 87,651
Amounts reclassified from accumulated other comprehensive income (loss) for the period ended December 31, 2013 | Amortization/settlement of pension and other postretirement benefits
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Pension settlement charges	63	(53,213)
Other income (expense), net	(315)	(504)
Income tax (expense) benefit	56	9,393
Net income	(196)	(44,324)
Amounts reclassified from accumulated other comprehensive income (loss) for the period ended December 31, 2013 | Unrealized gain (loss) on derivative instruments
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Other income (expense), net	(3,191)	200
Income tax (expense) benefit	715	(45)
Net income	$ (2,476)	$ 155