Fair value measurements - Fair Value, by Balance Sheet Grouping (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023
Fair value, balance sheet grouping [Line Items]
Long-term debt	$ 2,386,397	$ 2,298,223	$ 2,239,717
Carrying amount
Fair value, balance sheet grouping [Line Items]
Long-term debt	2,386,397	2,298,223	2,239,718
Fair value
Fair value, balance sheet grouping [Line Items]
Long-term debt, fair value	$ 2,098,002	$ 2,046,039	$ 1,974,344