Revenue - Subscription, Advertising, and Other Revenues (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 28, 2020	Jun. 30, 2019	Jun. 28, 2020	Jun. 30, 2019
Disaggregation of Revenue [Line Items]
Total revenues	$ 403,750	$ 436,258	$ 847,386	$ 875,320
Subscription
Disaggregation of Revenue [Line Items]
Total revenues	293,189	270,456	578,623	541,266
Advertising
Disaggregation of Revenue [Line Items]
Total revenues	67,760	120,761	173,897	245,849
Other
Disaggregation of Revenue [Line Items]
Total revenues	42,801	45,041	94,866	88,205
Real Estate
Disaggregation of Revenue [Line Items]
Revenue not from contract with customer	$ 7,000	$ 7,000	$ 15,000	$ 15,000
Product concentration risk | Product and service benchmark
Disaggregation of Revenue [Line Items]
As % of total	100.00%	100.00%	100.00%	100.00%
Product concentration risk | Product and service benchmark | Subscription
Disaggregation of Revenue [Line Items]
As % of total	72.60%	62.00%	68.30%	61.80%
Product concentration risk | Product and service benchmark | Advertising
Disaggregation of Revenue [Line Items]
As % of total	16.80%	27.70%	20.50%	28.10%
Product concentration risk | Product and service benchmark | Other
Disaggregation of Revenue [Line Items]
As % of total	10.60%	10.30%	11.20%	10.10%