| Commitments and contingencies - Narrative (Details) $ in Millions | Sep. 30, 2021  USD ($) | 
|---|---|
| Loss Contingencies [Line Items] | |
| Performance bond commitments | $ 36.1 | 
| Settled Litigation | |
| Loss Contingencies [Line Items] | |
| Disallowance | 7.3 | 
| Pending Litigation | |
| Loss Contingencies [Line Items] | |
| Disallowance | $ 19.9 | 
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- Definition Loss Contingency, Disallowed Amount No definition available. 
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- Definition The current carrying amount of the liability for the freestanding or embedded guarantor's obligations under the guarantee or each group of similar guarantees. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. No definition available. 
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- Details 
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