Document And Entity Information	9 Months Ended
Sep. 30, 2011	Oct. 28, 2011 Class A [Member]	Oct. 28, 2011 Class B [Member]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2011
Document Fiscal Year Focus	2011
Document Fiscal Period Focus	Q3
Entity Filer Category	Non-accelerated Filer
Entity Registrant Name	COMPX INTERNATIONAL INC
Entity Central Index Key	0001049606
Current Fiscal Year End Date	--12-31
Entity Common Stock, Shares Outstanding		2,386,107	10,000,000

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