Segment Information (Segment Operating Profit) (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Segment Information [Line Items]
Segment operating profit	$ 68,148	$ 78,699	$ 216,854	$ 256,010
Corporate, general, and administrative expenses	(37,741)	(43,633)	(120,653)	(123,486)
Interest and financing expenses, net	(7,807)	(5,564)	(18,536)	(16,496)
Other income (expense), net	7,973	3,842	20,872	10,986
Income before income tax expense	68,314	76,977	219,190	250,500
Operating Segments [Member]
Segment Information [Line Items]
Segment operating profit	73,529	85,266	229,528	273,784
Operating Segments [Member] \| Petroleum Additives [Member]
Segment Information [Line Items]
Segment operating profit	75,824	84,173	231,494	270,841
Operating Segments [Member] \| All Other [Member]
Segment Information [Line Items]
Segment operating profit	(2,295)	1,093	(1,966)	2,943
Corporate, Non-Segment [Member]
Segment Information [Line Items]
Corporate, general, and administrative expenses	(5,402)	(6,534)	(16,033)	(17,561)
Other income (expense), net	$ 7,994	$ 3,809	$ 24,231	$ 10,773

Amount of income (loss) from continuing operations, including income (loss) from equity method investments, before deduction of income tax expense (benefit), and income (loss) attributable to noncontrolling interest.

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