Description of business, basis of presentation and summary of significant accounting policies - Schedule of Disaggregation of Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Total revenues	$ 2,937,780	$ 2,299,497	$ 2,207,282
Subscription
Disaggregation of Revenue [Line Items]
Total revenues	1,286,611	1,005,030	840,838
Advertising & Marketing Services
Disaggregation of Revenue [Line Items]
Total revenues	1,174,774	1,226,607	1,106,754
Political
Disaggregation of Revenue [Line Items]
Total revenues	445,535	38,478	233,613
Other
Disaggregation of Revenue [Line Items]
Total revenues	$ 30,860	$ 29,382	$ 26,077