Noncontrolling Interest in Subsidiaries - Noncontrolling Interest in Net Assets of Subsidiaries (Detail) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Noncontrolling interest in net assets:
Noncontrolling interest in subsidiaries	$ 365.0	$ 342.3
Kronos Worldwide, Inc.
Noncontrolling interest in net assets:
Noncontrolling interest in subsidiaries	228.1	204.9
NL Industries
Noncontrolling interest in net assets:
Noncontrolling interest in subsidiaries	63.7	71.1
CompX International
Noncontrolling interest in net assets:
Noncontrolling interest in subsidiaries	19.2	17.8
BMI
Noncontrolling interest in net assets:
Noncontrolling interest in subsidiaries	28.0	26.0
LandWell
Noncontrolling interest in net assets:
Noncontrolling interest in subsidiaries	$ 26.0	$ 22.5

Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which is directly or indirectly attributable to that ownership interest in subsidiary equity which is not attributable to the parent (that is, noncontrolling interest, previously referred to as minority interest).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(24))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.31)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(22))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant