Business segment - Additional Information (Details) $ in Millions	12 Months Ended
	Dec. 31, 2025 USD ($) segment	Dec. 31, 2024 USD ($)
Segment Reporting, Asset Reconciling Item [Line Items]
Number of operating segments | segment	1
Number of reportable segments | segment	1
Assets | $	$ 1,139	$ 1,150
Reportable segment
Segment Reporting, Asset Reconciling Item [Line Items]
Assets | $	$ 1,100	$ 1,200