Segment Information - Summary of Tangible and Intangible Assets by Segments (Detail) - USD ($) $ in Millions		Mar. 31, 2020	Dec. 31, 2019
Segment Reporting Asset Reconciling Item [Line Items]
Assets	[1]	$ 1,573.1	$ 1,564.6
Goodwill		292.7	296.1
Railroad and Utility Products and Services [Member] | Operating Segments [Member]
Segment Reporting Asset Reconciling Item [Line Items]
Assets		572.4	562.2
Goodwill		120.2	120.7
Performance Chemicals [Member] | Operating Segments [Member]
Segment Reporting Asset Reconciling Item [Line Items]
Assets		468.5	457.7
Goodwill		172.5	175.4
Carbon Materials and Chemicals [Member] | Operating Segments [Member]
Segment Reporting Asset Reconciling Item [Line Items]
Assets		485.5	502.1
All Other [Member] | Operating Segments [Member]
Segment Reporting Asset Reconciling Item [Line Items]
Assets		$ 46.7	$ 42.6

[1]   (a) The Carbon Materials and Chemicals segment includes $67.5 million and $76.4 million of discontinued operations assets held for sale related to our KJCC business at March 31, 2020 and December 31, 2019, respectively.