Retirement plans - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
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	$ 18,700,000	$ 17,100,000	$ 16,500,000
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	79.00%
Contribution by employer	$ 2,700,000	2,900,000	$ 2,400,000
Retirement Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Actuarial gain	$ 119,462,000	$ 18,246,000
Discount rate	5.50%	2.89%	2.54%
Actuarial gain (losses) from change in discount rate	$ 120,100,000	$ 22,100,000
Accumulated benefit obligation	464,309,000	605,817,000
Contributions made to SERP	5,788,000	$ 6,337,000
Contributions expected to be made during next fiscal year	$ 5,500,000
Target Allocation	100.00%
Actual rate of return on plan assets (as a percent)	(23.00%)	4.50%	23.50%
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%
SERP
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Contributions made to SERP	$ 5,800,000