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

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
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=124440162&loc=d3e12069-110248

Name:	us-gaap_GuaranteeObligationsCurrentCarryingValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant