Revenue - Subscription, Advertising, and Other Revenues (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jul. 01, 2018	Jun. 30, 2019	Jul. 01, 2018
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 436,258	$ 414,560	$ 875,320	$ 828,508
Subscription
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	270,456	260,629	541,266	521,222
Advertising
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	120,761	119,201	245,849	244,848
Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	45,041	34,730	88,205	62,438
Real Estate
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 7,000	$ 6,000	$ 15,000	$ 10,000