Integration and reorganization costs and impairments of property, plant and equipment - Facility Consolidation Charges and Accelerated Depreciation (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Restructuring Cost and Reserve
Integration and reorganization costs	$ 32,306	$ 4,278	$ 60,560	$ 10,077
Facility Closing
Restructuring Cost and Reserve
Integration and reorganization costs	6,564	1,398	13,039	3,784
Operating Segments | Publishing | Facility Closing
Restructuring Cost and Reserve
Integration and reorganization costs	1,477	1,398	2,509	1,803
Operating Segments | Marketing Solutions | Facility Closing
Restructuring Cost and Reserve
Integration and reorganization costs	209	0	214	0
Corporate and Other | Facility Closing
Restructuring Cost and Reserve
Integration and reorganization costs	$ 4,878	$ 0	$ 10,316	$ 1,981