Acquisitions - Purchase Price Allocation (Detail) - USD ($) $ in Millions	Oct. 15, 2018	Aug. 10, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Business Acquisition [Line Items]
Goodwill			$ 3,722	$ 3,781	$ 3,753
Reis Inc
Business Acquisition [Line Items]
Current assets	$ 32
Property and equipment	4
Total intangible assets	104
Goodwill	183
Deferred tax assets	13
Deferred revenue	(14)
Accounts payable and accrued liabilities	(20)
Deferred tax liabilities	(24)
Total liabilities	(58)
Net assets acquired	$ 278
Weighted average life of intangible assets acquired (in years)	12 years
Reis Inc | Customer relationships
Business Acquisition [Line Items]
Total intangible assets	$ 77
Weighted average life of intangible assets acquired (in years)	14 years
Reis Inc | Database
Business Acquisition [Line Items]
Total intangible assets	$ 13
Weighted average life of intangible assets acquired (in years)	5 years
Reis Inc | Product Technology
Business Acquisition [Line Items]
Total intangible assets	$ 10
Weighted average life of intangible assets acquired (in years)	7 years
Reis Inc | Trade names
Business Acquisition [Line Items]
Total intangible assets	$ 4
Weighted average life of intangible assets acquired (in years)	10 years
Bureau Van Dijk
Business Acquisition [Line Items]
Current assets		$ 158
Property and equipment		4
Total intangible assets		1,353
Goodwill		2,615
Other assets		6
Deferred revenue		(101)
Accounts payable and accrued liabilities		(44)
Deferred tax liabilities		(330)
Other liabilities		(119)
Total liabilities		(594)
Net assets acquired		$ 3,542
Weighted average life of intangible assets acquired (in years)		21 years
Bureau Van Dijk | Customer relationships
Business Acquisition [Line Items]
Total intangible assets		$ 999
Weighted average life of intangible assets acquired (in years)		23 years
Bureau Van Dijk | Database
Business Acquisition [Line Items]
Total intangible assets		$ 13
Weighted average life of intangible assets acquired (in years)		10 years
Bureau Van Dijk | Product Technology
Business Acquisition [Line Items]
Total intangible assets		$ 259
Weighted average life of intangible assets acquired (in years)		12 years
Bureau Van Dijk | Trade names
Business Acquisition [Line Items]
Total intangible assets		$ 82
Weighted average life of intangible assets acquired (in years)		18 years