Leases - Quantitative information (Details) - USD ($) $ in Millions |
3 Months Ended | 9 Months Ended | ||
---|---|---|---|---|
Sep. 30, 2020 |
Sep. 30, 2019 |
Sep. 30, 2020 |
Sep. 30, 2019 |
|
Lessee, Lease, Description [Line Items] | ||||
Option to renew | true | |||
Weighted average remaining lease term for operating leases | 3 months 7 days | 3 months 7 days | ||
Weighted average discount rate used to measure operating lease liabilities | 4.48% | 4.48% | ||
Operating lease, existence of material residual value guarantees | false | |||
Inventory | ||||
Lessee, Lease, Description [Line Items] | ||||
Capitalized variable lease costs | $ 1.8 | $ 0.3 | $ 4.6 | $ 1.8 |
Property, plant and mine development | ||||
Lessee, Lease, Description [Line Items] | ||||
Capitalized variable lease costs | $ 1.4 | $ 1.5 | $ 3.2 | |
Maximum | ||||
Lessee, Lease, Description [Line Items] | ||||
Renewal term | 2 years | 2 years | ||
Minimum | ||||
Lessee, Lease, Description [Line Items] | ||||
Renewal term | 1 year | 1 year |