Document And Entity Information	3 Months Ended
	Mar. 31, 2012	May 03, 2012 Common Stock Class A [Member]	May 03, 2012 Common Stock Class B [Member]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2012
Document Fiscal Year Focus	2012
Document Fiscal Period Focus	Q1
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