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v3.19.1

Related Party Transactions - Additional Information (Details) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2018 | Dec. 31, 2017
Related Party Transaction [Line Items] |  |
Balance with Fund Manager | $ 16,270 | $ 14,842
Investment income generated from mutual funds | $ (28) | $ 21
Minimum [Member] |  |
Related Party Transaction [Line Items] |  |
Percentage of stockholders controlling a related party | 10.00% | 10.00%
Maximum [Member] |  |
Related Party Transaction [Line Items] |  |
Fund management fee percent | 0.25% |
Other Income [Member] |  |
Related Party Transaction [Line Items] |  |
Investment income generated from mutual funds | $ 203 |
Cash and Cash Equivalents [Member] |  |
Related Party Transaction [Line Items] |  |
Balance with Fund Manager | 12,506 | $ 11,050
Marketable Securities [Member] |  |
Related Party Transaction [Line Items] |  |
Balance with Fund Manager | $ 3,764 | $ 3,792

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- Definition Fund management fee percent. + References No definition available. + Details
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Namespace Prefix: | lgl_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

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- Definition Element represents the percentage of stockholders controlling a related party. + References No definition available. + Details
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Namespace Prefix: | lgl_
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Balance Type: | na
Period Type: | instant

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- Definition The carrying amount of assets an investment adviser manages on behalf of investors. + References No definition available. + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
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- Definition Amount of unrealized and realized gain (loss) on investment in marketable security, including other-than-temporary impairment (OTTI). + References No definition available. + Details
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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Balance Type: | na
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- Details
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Period Type: |

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- Details
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- Details
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Balance Type: |
Period Type: |

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- Details
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Namespace Prefix: |
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Balance Type: |
Period Type: |

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- Details
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Namespace Prefix: |
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Balance Type: |
Period Type: |