Accounting And Reporting Policies (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) Customer Segment shares	Dec. 31, 2016 USD ($) Customer shares
Property, Plant and Equipment, Net [Abstract]
Depreciation expense	$ 567	$ 704
Standard Product Warranty Disclosure [Abstract]
Term of warranty	1 year
Accrued Warranty Expense	$ 10	80
Intangible Assets [Abstract]
Intangible assets carrying value	512	588
Goodwill	40	40
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
2018	75
2019	75
2020	75
2021	75
2022	75
Thereafter	137
Total	512	588
Research and Development Costs [Abstract]
Research and development costs	1,827	1,906
Advertising Expense [Abstract]
Advertising costs	$ 18	$ 50
Weighted Average Number of Shares Outstanding Reconciliation [Abstract]
Weighted average shares outstanding - basic | shares	2,929,641	2,665,043
Effect of diluted securities | shares	105,463	687
Weighted average shares outstanding - diluted | shares	3,035,104	2,665,730
Income Taxes [Abstract]
Deferred tax assets	$ 173	$ 214
Concentration Risk [Line Items]
Revenue concentration greater than 10%	$ 22,402	20,891
Segment Reporting Information [Line Items]
Number of identified reportable segments | Segment	2
Foreign Currency Translation [Abstract]
Re-measurement loss	$ 22	(2)
Revenues [Member] | Customer Concentration Risk [Member]
Concentration Risk [Line Items]
Revenue concentration greater than 10%	$ 3,744	$ 3,275
Concentration risk, percentage	16.70%	15.70%
Accounts Receivable [Member] | Customer Concentration Risk [Member]
Concentration Risk [Line Items]
Concentration risk, percentage	32.00%	35.10%
Accounts receivable	$ 1,100	$ 1,242
Number of large customers | Customer	4	4
Foreign NOLs [Member]
Income Taxes [Abstract]
Deferred tax assets	$ 173
Options [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Securities excluded from the diluted earnings per share computation (in shares) | shares	42,676	166,996
Warrant [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Securities excluded from the diluted earnings per share computation (in shares) | shares	519,241	519,241
Maximum [Member]
Intangible Assets [Abstract]
Estimated useful life of intangible assets	10 years
Buildings and Improvements [Member] | Minimum [Member]
Property, Plant and Equipment, Net [Abstract]
Property, Plant and Equipment, Useful Life	5 years
Buildings and Improvements [Member] | Maximum [Member]
Property, Plant and Equipment, Net [Abstract]
Property, Plant and Equipment, Useful Life	35 years
Other Fixed Assets [Member] | Minimum [Member]
Property, Plant and Equipment, Net [Abstract]
Property, Plant and Equipment, Useful Life	3 years
Other Fixed Assets [Member] | Maximum [Member]
Property, Plant and Equipment, Net [Abstract]
Property, Plant and Equipment, Useful Life	10 years
M-tron Industries, Inc. [Member]
Subsidiaries of the entity, by ownership percentage [Abstract]
Owned by The LGL Group, Inc.	100.00%
Piezo Technology, Inc. [Member]
Subsidiaries of the entity, by ownership percentage [Abstract]
Owned by The LGL Group, Inc.	100.00%
Piezo Technology India Private Ltd. [Member]
Subsidiaries of the entity, by ownership percentage [Abstract]
Owned by The LGL Group, Inc.	99.00%
M-tron Asia LLC [Member]
Subsidiaries of the entity, by ownership percentage [Abstract]
Owned by The LGL Group, Inc.	100.00%
M-tron Industries, Ltd. [Member]
Subsidiaries of the entity, by ownership percentage [Abstract]
Owned by The LGL Group, Inc.	100.00%
GC Opportunities Ltd. [Member]
Subsidiaries of the entity, by ownership percentage [Abstract]
Owned by The LGL Group, Inc.	100.00%
M-tron Services Ltd [Member]
Subsidiaries of the entity, by ownership percentage [Abstract]
Owned by The LGL Group, Inc.	100.00%
Precise Time and Frequenc, LLC [Member]
Subsidiaries of the entity, by ownership percentage [Abstract]
Owned by The LGL Group, Inc.	100.00%
Lynch Systems, Inc. [Member]
Subsidiaries of the entity, by ownership percentage [Abstract]
Owned by The LGL Group, Inc.	100.00%