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Discontinued Operations and Assets Held for Sale - Asphalt Terminals Held for Sale (Details)
$ in Millions
3 Months Ended 6 Months Ended
May 21, 2018
USD ($)
asphalt_terminal
Jun. 30, 2018
USD ($)
Jun. 30, 2017
USD ($)
Jun. 30, 2018
USD ($)
Jun. 30, 2017
USD ($)
Feb. 12, 2018
USD ($)
asphalt_terminal
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]            
Proceeds from sale of equity method investment $ 110.8          
Impairment loss on assets held for sale   $ 0.0 $ 0.0 $ 27.5 $ 0.0  
(Gain) loss on sale of business   $ (13.2) $ 0.0 $ (13.2) $ 0.0  
Four Asphalt Terminals [Member]            
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]            
Number Of Asphalt Terminals | asphalt_terminal 4         4
Consideration of business disposition           $ 75.0
Paramount-Nevada Asphalt Company, LLC [Member]            
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]            
Equity method investment, ownership percentage (as percent) 50.00%         50.00%