| Document and Entity Information | Dec. 28, 2021 |
| Document Information [Line Items] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Dec. 28, 2021 |
| Entity Registrant Name | THE LGL GROUP, INC. |
| Entity Central Index Key | 0000061004 |
| Current Fiscal Year End Date | --12-31 |
| Entity File Number | 001-00106 |
| Entity Incorporation, State or Country Code | DE |
| Entity Tax Identification Number | 38-1799862 |
| Entity Emerging Growth Company | false |
| Entity Address, Address Line One | 2525 Shader Road |
| Entity Address, City or Town | Orlando |
| Entity Address, State or Province | FL |
| Entity Address, Postal Zip Code | 32804 |
| City Area Code | 407 |
| Local Phone Number | 298-2000 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Common Stock [Member] | |
| Document Information [Line Items] | |
| Trading Symbol | LGL |
| Title of 12(b) Security | Common Stock, par value $0.01 |
| Security Exchange Name | NYSE |
| Warrants To Purchase Common Stock [Member] | |
| Document Information [Line Items] | |
| Trading Symbol | LGL WS |
| Title of 12(b) Security | Warrants to Purchase Common Stock, par value $0.01 |
| Security Exchange Name | NYSE |
