Fair value measurements - Fair Value, by Balance Sheet Grouping (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023	Jun. 30, 2023
Fair value, balance sheet grouping [Line Items]
Long-term debt	$ 2,400,617	$ 2,298,223	$ 2,247,422
Carrying amount
Fair value, balance sheet grouping [Line Items]
Long-term debt	2,400,617	2,298,223	2,247,422
Fair value
Fair value, balance sheet grouping [Line Items]
Long-term debt, fair value	$ 2,087,677	$ 2,046,039	$ 1,949,905

Amount, after deduction of unamortized premium (discount) and debt issuance cost, of long-term debt. Excludes lease obligation.

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