Segment Information - Summary of Tangible and Intangible Assets by Segments (Detail) - USD ($) $ in Millions		Sep. 30, 2019	Dec. 31, 2018
Segment Reporting Asset Reconciling Item [Line Items]
Assets	[1]	$ 1,553.4	$ 1,479.9
Goodwill		294.8	296.5
Railroad and Utility Products and Services [Member] | Operating Segments [Member]
Segment Reporting Asset Reconciling Item [Line Items]
Assets		557.2	538.0
Goodwill		120.6	121.1
Performance Chemicals [Member] | Operating Segments [Member]
Segment Reporting Asset Reconciling Item [Line Items]
Assets		461.6	446.9
Goodwill		174.2	175.4
Carbon Materials and Chemicals [Member] | Operating Segments [Member]
Segment Reporting Asset Reconciling Item [Line Items]
Assets		481.6	457.1
All Other [Member] | Operating Segments [Member]
Segment Reporting Asset Reconciling Item [Line Items]
Assets		$ 53.0	$ 37.9

[1]   (a) Increase in total assets as of September 30, 2019 includes $116.0 million attributable to the implementation of ASU No. 2016-02 “Leases (Topic 842).”