Document And Entity Information - shares	9 Months Ended
	Sep. 30, 2026	Oct. 30, 2026
Document Information [Line Items]
Entity Central Index Key	0000061004
Entity Registrant Name	LGL GROUP INC
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Document Fiscal Period Focus	Q3
Document Fiscal Year Focus	2026
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2026
Document Transition Report	false
Entity File Number	001-00106
Entity Incorporation, State or Country Code	NV
Entity Tax Identification Number	38-1799862
Entity Address, Address Line One	3100 Clarendon Blvd, Suite 1200
Entity Address, City or Town	Arlington
Entity Address, State or Province	VA
Entity Address, Postal Zip Code	22201
City Area Code	571
Local Phone Number	543-1946
Title of 12(b) Security	Common Stock, par value $0.01
Trading Symbol	LGL
Security Exchange Name	NYSE
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		12,613,149