Employee Benefit Plans - Additional Information (Details) - USD ($)	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Compensation And Retirement Disclosure [Abstract]
Employer matching contribution, percentage	50.00%
Employer matching contribution of employees' contribution, percentage	6.00%
Employer matching contribution amount	$ 115,000	$ 118,000
Annual vesting percentage of employer contributions	20.00%
Vesting period of employer matching contributions	6 years
Vesting percentage of employer contributions by year six	100.00%

Vesting period of employer's matching contributions to a defined contribution plan.

No definition available.

Name:	lgl_DefinedContributionPlanEmployersMatchingContributionVestingPeriod
Namespace Prefix:	lgl_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

The vesting percentage of employer contributions by the sixth year of participating in the defined contribution plan.

No definition available.

Name:	lgl_VestingPercentageOfEmployerContributionsByYearSix
Namespace Prefix:	lgl_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

No definition available.

Name:	us-gaap_CompensationAndRetirementDisclosureAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Amount of discretionary contributions made by an employer to a defined contribution plan.

No definition available.

Name:	us-gaap_DefinedContributionPlanEmployerDiscretionaryContributionAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Percentage of employees' gross pay for which the employer contributes a matching contribution to a defined contribution plan.

No definition available.

Name:	us-gaap_DefinedContributionPlanEmployerMatchingContributionPercent
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Percentage of employer's matching contributions to a defined contribution plan that vests in a given year.

No definition available.

Name:	us-gaap_DefinedContributionPlanEmployersMatchingContributionAnnualVestingPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Maximum percentage of employee gross pay the employee may contribute to a defined contribution plan.

No definition available.

Name:	us-gaap_DefinedContributionPlanMaximumAnnualContributionsPerEmployeePercent
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration