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Fair Value Measurements - Financial Assets and Liabilities Carried at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands |  | 3 Months Ended | 9 Months Ended |
--- | --- | --- | --- | ---
Jun. 30, 2021 | Sep. 30, 2020 | Sep. 30, 2021 | Sep. 30, 2020 | Dec. 31, 2020
Transfers between Levels |  |  |  |  |
Transfer into Level 3 |  | $ 0 |  | $ 0 |
Transfer out of Level 3 | $ 2,310 | 0 |  | 0 |
Level 2 to Level 1 transfers, Assets |  | 0 |  | 0 |
Level 1 to Level 2 transfers, Liabilities |  | 0 |  | 0 |
Level 2 to Level 1 transfers, Liabilities |  | $ 0 |  | $ 0 |
Significant Unobservable Inputs (Level 3) [Member] |  |  |  |  |
Transfers between Levels |  |  |  |  |
Transfer out of Level 3 |  |  | $ 2,310 |  |
Recurring [Member] |  |  |  |  |
Assets: |  |  |  |  |
Equity securities |  |  | 1,211 |  | $ 1,693
Liabilities: |  |  |  |  |
Contingent consideration |  |  | 75 |  | 75
Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] |  |  |  |  |
Assets: |  |  |  |  |
Equity securities |  |  | 1,211 |  |
Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] |  |  |  |  |
Assets: |  |  |  |  |
Equity securities |  |  |  |  | 1,693
Liabilities: |  |  |  |  |
Contingent consideration |  |  | $ 75 |  | $ 75

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