Segment Information - Summary of Tangible and Intangible Assets by Segments ((Parenthetical)) (Detail) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Segment Reporting Asset Reconciling Item [Line Items]
Fair value	$ 68.1	$ 76.4
Discontinued Operations, Held-for-sale [Member] \| Carbon Materials and Chemicals [Member]
Segment Reporting Asset Reconciling Item [Line Items]
Fair value	$ 68.1	$ 76.4

Amount classified as assets attributable to disposal group held for sale or disposed of.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant