Retirement plans - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Nov. 30, 2022	Dec. 31, 2021
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
401(k) employee maximum matching contribution (up to)	50.00%
401(k) employer matching contribution	100.00%
Contributions per employee subject to employer match	4.00%
Compensation expense related to 401(k) contributions	$ 18,600,000	$ 18,700,000		$ 17,100,000
Expenses incurred for multi-employer withdrawal liabilities	0	0		0
AFTRA Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Funded percentage			82.00%
Contribution by employer	2,800,000	2,700,000		$ 2,900,000
CBA contribution as a percent of total contribution			5.00%
Retirement Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Actuarial (loss) gain	$ (9,443,000)	$ 119,462,000
Discount rate	5.20%	5.50%		2.89%
Discount rate	5.50%	2.89%		2.54%
Actuarial gain (losses) from change in discount rate	$ (10,900,000)	$ 120,100,000
Contributions made to SERP	$ 3,833,000	$ 5,788,000
Target allocation	100.00%
Actual rate of return on plan assets (as a percent)	10.00%	(23.00%)		4.50%
Retirement Plans | Corporate stock
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Target allocation	14.00%
Retirement Plans | Debt securities
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Target allocation	86.00%
TRP
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Contributions expected to be made during next fiscal year	$ 6,900,000
SERP
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Contributions made to SERP	3,800,000
Contributions expected to be made during next fiscal year	$ 5,800,000