Acquisitions and Other Strategic Initiatives - Purchase Price Allocation (Details) - USD ($) $ in Millions	Feb. 13, 2020	Mar. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Business Acquisition [Line Items]
Goodwill		$ 4,122	$ 3,722	$ 3,781
Regulatory Data Corporation
Business Acquisition [Line Items]
Current assets	$ 24
Total intangible assets	280
Goodwill	494
Other assets	2
Accounts payable and accrued liabilities	(5)
Deferred revenue	(20)
Deferred tax liabilities	(71)
Other liabilities	(2)
Total liabilities	(98)
Net assets acquired	$ 702
Acquired finite-lived intangible asset, useful life	19 years
Regulatory Data Corporation | Customer relationships
Business Acquisition [Line Items]
Total intangible assets	$ 174
Acquired finite-lived intangible asset, useful life	25 years
Regulatory Data Corporation | Database
Business Acquisition [Line Items]
Total intangible assets	$ 86
Acquired finite-lived intangible asset, useful life	10 years
Regulatory Data Corporation | Product technology
Business Acquisition [Line Items]
Total intangible assets	$ 17
Acquired finite-lived intangible asset, useful life	4 years
Regulatory Data Corporation | Trade names
Business Acquisition [Line Items]
Total intangible assets	$ 3
Acquired finite-lived intangible asset, useful life	3 years