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Revenue Recognition (Details) - Revenues as a result of changes in the contract asset and the contract liability - USD ($)
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Revenue Recognition (Details) - Revenues as a result of changes in the contract asset and the contract liability [Line Items]    
Amounts included in the contract liability at the beginning of the period $ 82,000 $ 392,000
Performance obligations satisfied in previous periods (for example, due to changes in transaction price)