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Nature of Operations and Summary of Significant Accounting Policies - Impairment or Disposal of Long-Lived Assets (Details) - USD ($)
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Nature of Operations and Summary of Significant Accounting Policies      
Asset Impairment Charges $ 0 $ 0 $ 0