Amount of gain (loss), before tax expense or benefit and not previously recognized, resulting from the sale of a business component.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 144

-Paragraph 47

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 205

-SubTopic 20

-Section 45

-Paragraph 3

-URI http://asc.fasb.org/extlink&oid=6892542&loc=d3e957-107759

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 144

-Paragraph 43

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 205

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6360339&loc=d3e1361-107760

Business combinations, discontinued operations and related transactions - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	1 Months Ended	3 Months Ended								12 Months Ended			1 Months Ended	12 Months Ended		12 Months Ended			1 Months Ended
	May 31, 2012	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	May 31, 2011 Kronos Worldwide, Inc. [Member]	Dec. 31, 2010 Kronos Worldwide, Inc. [Member]	Dec. 31, 2012 Kronos Worldwide, Inc. [Member]	Dec. 31, 2012 CompX [Member]	Dec. 31, 2012 CompX [Member] Discontinued operations [Member]	Dec. 31, 2012 Class A [Member] CompX [Member]	Nov. 30, 2010 Secondary Public Common Stock Offering [Member] Kronos Worldwide, Inc. [Member]	Nov. 30, 2010 Secondary Public Common Stock Offering [Member] Kronos Worldwide, Inc. [Member] NL [Member]
Business Combinations Discontinued Operations And Related Transactions [Line Items]
Secondary public offering																			17,940,000
Net proceeds from new issuance of common stock																			$ 337.6
Public offering price																			$ 20.00
Percentage of underwriting discount																			5.75%
Underwriting discount price																			$ 1.15
Cost of offerings																			0.7
Total controlling interest															80.00%	87.00%			80.00%
Direct controlling interest in subsidiary															50.00%					50.00%
Indirect controlling interest in subsidiary															30.00%				30.00%
Repurchase of common stock														2,000,000
Shares available for purchase															2,000,000			678,000
Stock split	3-for-1												2-for-1
Sale of Furniture Components segment										58.0	0.3	0.5					58.0
Gain on sale of discontinued operations										23.7							23.7
Gain on sale discontinued operations, net of tax																	15.7
Net income tax gain from disposal of discontinued operation per basic and diluted share		$ 0.01	$ 0.07	$ 0.13	$ 0.26	$ 0.16	$ 0.21	$ 0.15	$ 0.11	$ 0.47	$ 0.64	$ 0.14					$ 0.05
Reclassification out of AOCI, foreign currency translation adjustment										(7.2)				9.0			10.4
Statutory income tax rate of foreign tax credit										35.00%	35.00%	35.00%				35.00%
Promissory notes issued																	$ 3.0