Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended				12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Mar. 31, 2017	Dec. 31, 2017
Income Tax Disclosure [Line Items]
U.S. federal corporate income tax rate	21.00%			35.00%	35.00%
Dividends received from Kronos Worldwide, Inc.	$ 5,987			$ 5,283
Deferred income tax benefit from change in enacted tax rate					$ (37,500)
Kronos
Income Tax Disclosure [Line Items]
Dividends received from Kronos Worldwide, Inc.	6,000			5,300
Kronos | German | Corporate Tax Purposes
Income Tax Disclosure [Line Items]
Net operating loss carryforwards		$ 652,000			652,000
Kronos | German | Trade Tax Purposes
Income Tax Disclosure [Line Items]
Net operating loss carryforwards		500			500
Kronos | Belgium | Corporate Tax Purposes
Income Tax Disclosure [Line Items]
Net operating loss carryforwards		50,000			50,000
Kronos | Non-US | Current Periods Net Operating Loss Utilization
Income Tax Disclosure [Line Items]
Increase (decrease) in non-cash deferred income tax asset valuation allowance				$ (5,000)
Kronos | European and Candadian Subsidiaries | Undistributed Earnings Previously Considered to be Permanently Reinvested
Income Tax Disclosure [Line Items]
Aggregate provisional non-cash deferred income tax expense (benefit)	$ 4,000	4,500
Kronos European Subsidiaries | Transition Tax
Income Tax Disclosure [Line Items]
Currently payable (receivable)		$ 76,200
Current income tax expense payment period		8 years
Current income tax expense payable in next fiscal year		$ 6,100			6,100
Current income tax expense payable in increments over remainder of eight year period		$ 70,100			$ 70,100
Kronos Canadian Subsidiary | Canada-Germany APA | Canada Revenue Agency | Earliest Tax Year
Income Tax Disclosure [Line Items]
Effective tax year			2005
Kronos Canadian Subsidiary | Canada-Germany APA | Canada Revenue Agency | Latest Tax Year
Income Tax Disclosure [Line Items]
Effective tax year			2017
Kronos German Subsidiary | Germany- Canada APA | Germany Revenue Agency | Earliest Tax Year
Income Tax Disclosure [Line Items]
Effective tax year	2005
Kronos German Subsidiary | Germany- Canada APA | Germany Revenue Agency | Latest Tax Year
Income Tax Disclosure [Line Items]
Effective tax year	2017
Kronos Canadian And German Subsidiaries | Germany- Canada APA
Income Tax Disclosure [Line Items]
Non-cash income tax benefit	$ 1,400