Segment Information - Schedule of Segment Revenues for Significant Product Lines (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Net sales	$ 425,400	$ 442,700	$ 436,000	$ 406,100	$ 366,100	$ 384,800	$ 378,000	$ 346,600	$ 1,710,200	$ 1,475,500	$ 1,416,200
Railroad and Utility Products and Services [Member]
Segment Reporting Information [Line Items]
Net sales									634,800	512,600	586,500
Railroad and Utility Products and Services [Member] | Railroad Treated Products [Member]
Segment Reporting Information [Line Items]
Net sales									341,700	380,400	435,900
Railroad and Utility Products and Services [Member] | Utility Poles [Member]
Segment Reporting Information [Line Items]
Net sales									184,700	46,000	42,100
Railroad and Utility Products and Services [Member] | Rail Joints [Member]
Segment Reporting Information [Line Items]
Net sales									33,500	28,200	24,400
Railroad and Utility Products and Services [Member] | Railroad Infrastructure Services [Member]
Segment Reporting Information [Line Items]
Net sales									36,900	34,800	43,400
Railroad and Utility Products and Services [Member] | Other Products [Member]
Segment Reporting Information [Line Items]
Net sales									38,000	23,200	40,700
Carbon Materials and Chemicals [Member]
Segment Reporting Information [Line Items]
Net sales									655,400	551,700	436,300
Carbon Materials and Chemicals [Member] | Other Products [Member]
Segment Reporting Information [Line Items]
Net sales									42,800	63,500	24,800
Carbon Materials and Chemicals [Member] | Pitch and Related Products [Member]
Segment Reporting Information [Line Items]
Net sales									403,100	275,800	232,900
Carbon Materials and Chemicals [Member] | Creosote and Distillates [Member]
Segment Reporting Information [Line Items]
Net sales									84,100	83,700	73,200
Carbon Materials and Chemicals [Member] | Phthalic Anhydride and Other Chemicals [Member]
Segment Reporting Information [Line Items]
Net sales									84,600	89,800	73,300
Carbon Materials and Chemicals [Member] | Naphthalene [Member]
Segment Reporting Information [Line Items]
Net sales									40,800	38,900	32,100
Performance Chemicals [Member]
Segment Reporting Information [Line Items]
Net sales									420,000	411,200	393,400
Performance Chemicals [Member] | Other Products [Member]
Segment Reporting Information [Line Items]
Net sales									48,700	27,400	27,900
Performance Chemicals [Member] | Wood Preservative Products [Member]
Segment Reporting Information [Line Items]
Net sales									$ 371,400	$ 383,800	$ 365,500