Commitments and contingencies - Property in development commitment (Details) - Property, in development commitment - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020
Other Commitments [Line Items]
Future payments relating to the construction and retrofit of the building	$ 5.6
Total aggregate remaining minimum commitment	$ 6.1	$ 4.9

Amount of commitment classified as other to be paid in next fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

No definition available.

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