Business segment data - Operating Revenues Reconciliation (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	$ 1,213,825	$ 1,430,098
Operating Segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	1,244,291	1,456,465
Corporate, Non-Segment
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	1,433	1,572
Intersegment eliminations
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenues	$ (31,899)	$ (27,939)