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Revenue Recognition (Unearned Revenue) (Details)
$ in Millions
Dec. 31, 2020
USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01  
Disaggregation of Revenue [Line Items]  
Unearned revenue $ 2.3
Expected timing of satisfaction 12 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01  
Disaggregation of Revenue [Line Items]  
Unearned revenue $ 0.7
Expected timing of satisfaction 12 months