Amount of net assets (liabilities).

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The net amount (to the extent disclosed within this portion of the income statement) by which an insurance settlement exceeds incremental costs incurred from the event causing an interruption of business, plus the insurance award for earnings lost from the event, such as a natural catastrophe, explosion or fire.

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Business and Geographic Segments - Additional Information (Detail) $ in Millions	3 Months Ended			12 Months Ended
	Dec. 31, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2017 USD ($) Segment	Dec. 31, 2016 USD ($)
Segment Reporting Information [Line Items]
Number of operating segments \| Segment				3
Contract related intangible asset impairment			$ 5.1		$ 5.1
Business interruption insurance proceeds	$ 0.9	$ 1.4	2.0		4.3
Non-U.S. subsidiaries
Segment Reporting Information [Line Items]
Net assets of non-U.S. subsidiaries	$ 374.0			$ 614.0	374.0
Real Estate Management And Development \| Customer Relationships
Segment Reporting Information [Line Items]
Contract related intangible asset impairment			$ 5.1		5.1
Chemicals
Segment Reporting Information [Line Items]
Business interruption insurance proceeds					$ 4.3
Kronos Worldwide, Inc.
Segment Reporting Information [Line Items]
Direct ownership percentage by parent				50.00%
Indirect controlling interest in subsidiary				30.00%
NL
Segment Reporting Information [Line Items]
Direct ownership percentage by parent				83.00%
LandWell
Segment Reporting Information [Line Items]
Direct ownership percentage by parent				27.00%
Indirect controlling interest in subsidiary				50.00%
BMI
Segment Reporting Information [Line Items]
Direct ownership percentage by parent				63.00%
BMI \| Real Estate Management And Development
Segment Reporting Information [Line Items]
Direct ownership percentage by parent				63.00%