Business segment data - Schedule of Operating Revenues Reconciliation (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	$ 315,036	$ 289,694	$ 1,341,055	$ 1,222,440
Operating Segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	319,535	293,660	1,389,191	1,265,850
Corporate, Non-Segment
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	182	22	540	82
Intersegment eliminations
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	$ (4,681)	$ (3,988)	$ (48,676)	$ (43,492)