Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2023	Apr. 26, 2023
Cover [Abstract]
Document Type	10-Q
Document Period End Date	Mar. 31, 2023
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity File Number	1-13905
Entity Registrant Name	COMPX INTERNATIONAL INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	57-0981653
Entity Address, Address Line One	5430 LBJ Freeway
Entity Address, Address Line Two	Suite 1700
Entity Address, City or Town	Dallas
Entity Address, State or Province	TX
Entity Address, Postal Zip Code	75240-2620
City Area Code	972
Local Phone Number	448-1400
Title of 12(b) Security	Class A common stock
Trading Symbol	CIX
Security Exchange Name	NYSEAMER
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		12,307,157
Document Quarterly Report	true
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	Q1
Amendment Flag	false
Entity Central Index Key	0001049606