Revenue Recognition - Remaining Performance Obligation (2) (Details) $ in Millions	Jun. 30, 2020 USD ($)
Harsco Metals and Minerals
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation	$ 98.7
Harsco Rail Segment
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation	$ 360.7