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Revenue - Significant Changes in Contract Liabilities (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Contract With Customer, Asset (Liability) [Roll Forward]    
Beginning balance $ (1.1) $ (0.9)
Payments received / amounts billed (0.9) (3.8)
Costs incurred / revenue recognized 1.5 3.6
Ending balance $ (0.5) $ (1.1)