Commitments and Contingencies - Additional Information (Details) - USD ($)	1 Months Ended	9 Months Ended
	Oct. 31, 2017	Sep. 30, 2017
Commitment And Contingencies [Line Items]
Effective date of agreement		Oct. 01, 2007
Subsequent Event
Commitment And Contingencies [Line Items]
Purchase amended and restated agreement date	Oct. 01, 2017
Purchase amended and restated agreement effective date	Jan. 01, 2017
Extended agreement term	5 years
Agreement expiration date	December 31, 2025
Period for renewal options granted	three one-year
Description of renewal options granted	The term of the Agreement has been extended for an additional five years, so as to expire on December 31, 2025, with three one-year renewal options granted to Nielsen.
Subsequent Event | Services Per Year From 2021 Through 2024
Commitment And Contingencies [Line Items]
Commitment to purchase services	$ 186,000,000
Subsequent Event | Services 2025
Commitment And Contingencies [Line Items]
Commitment to purchase services	139,500,000
Subsequent Event | Minimum | Services Per Year From 2017 Through 2020
Commitment And Contingencies [Line Items]
Commitment to purchase services	320,000,000
Subsequent Event | Commitment
Commitment And Contingencies [Line Items]
Purchase commitment, remaining minimum amount committed	$ 2,250,000,000