Income taxes - Schedule of Deferred Tax Liabilities and Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Deferred tax liabilities
Accelerated amortization of deductible intangibles	$ 561,741	$ 540,260
Accelerated depreciation	65,247	67,278
Right-of-use assets for operating leases	18,361	19,467
Other	4,024	4,183
Total deferred tax liabilities	649,373	631,188
Deferred tax assets
Accrued compensation costs	22,450	23,439
Pension and post-retirement medical and life	18,839	20,775
Loss carryforwards	16,435	12,537
Operating lease liabilities	19,443	20,403
Other	18,988	24,242
Total deferred tax assets	96,155	101,396
Deferred tax asset valuation allowance	25,001	26,339	$ 41,929	$ 43,467
Total net deferred tax liabilities	$ 578,219	$ 556,131