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Property, Plant and Equipment - Additional Information (Details) - USD ($)
$ in Millions
Jun. 30, 2019
Dec. 31, 2018
Proved Oil And Gas Properties    
Business Acquisition [Line Items]    
Estimate of future asset retirement costs $ 42.2 $ 40.5
Property, Plant and Equipment, Other Types    
Business Acquisition [Line Items]    
Estimate of future asset retirement costs $ 1.4 $ 1.3