Leases - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Lessee Lease Description [Line Items]
Operating lease, existence of option to extend	true
Rent expense under operating leases	$ 430,000	$ 393,000
Right-of-use lease assets in exchange for operating lease liabilities	318,000
Lease obligation payable	$ 331,000
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	lgl:OtherAccruedLabilitiesCurrentMember
Minimum [Member]
Lessee Lease Description [Line Items]
Operating lease renewal term	1 year
Term of operating leases	1 year
Maximum [Member]
Lessee Lease Description [Line Items]
Operating lease renewal term	10 years
Term of operating leases	5 years