Integration and reorganization costs and impairments of property, plant and equipment - Facility Consolidation Charges and Accelerated Depreciation (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 29, 2019	Sep. 30, 2020	Sep. 29, 2019
Restructuring Cost and Reserve
Integration and reorganization costs	$ 13,417	$ 3,136	$ 73,978	$ 13,213
Facility Closing
Restructuring Cost and Reserve
Integration and reorganization costs	6,135	1,208	19,175	4,992
Operating Segments | Publishing | Facility Closing
Restructuring Cost and Reserve
Integration and reorganization costs	1,137	1,119	3,648	2,922
Operating Segments | Marketing Solutions | Facility Closing
Restructuring Cost and Reserve
Integration and reorganization costs	41	70	254	70
Corporate and Other | Facility Closing
Restructuring Cost and Reserve
Integration and reorganization costs	$ 4,957	$ 19	$ 15,273	$ 2,000