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Goodwill (Details)
$ in Millions
3 Months Ended 12 Months Ended
Sep. 30, 2019
USD ($)
reportingUnit
Dec. 31, 2018
USD ($)
Dec. 31, 2019
USD ($)
reportingUnit
Dec. 31, 2020
USD ($)
Goodwill [Line Items]        
Goodwill   $ 65.1 $ 15.4 $ 10.5
Goodwill impairment $ 49.7 $ 37.2 $ 49.7  
Weighted average discount rate | Discounted cash flow analysis        
Goodwill [Line Items]        
Weighted average discount rate (percent)   13.60% 12.70%  
Materials and Construction Segment        
Goodwill [Line Items]        
Goodwill   $ 56.4 $ 6.7 $ 1.8
Number of Reporting Units | reportingUnit 3   3  
Goodwill impairment     $ 49.7