Restructuring - Summary (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Operating Segments | Ratings
Restructuring Cost and Reserve [Line Items]
Initial Charge Recorded	$ 11		$ 11
Operating Segments | Market Intelligence
Restructuring Cost and Reserve [Line Items]
Initial Charge Recorded		$ 2	1
Operating Segments | Platts
Restructuring Cost and Reserve [Line Items]
Initial Charge Recorded			1
Corporate
Restructuring Cost and Reserve [Line Items]
Initial Charge Recorded		10	$ 7
2020 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Initial Charge Recorded		12
Ending Reserve Balance		7
2020 Restructuring Plan | Operating Segments | Ratings
Restructuring Cost and Reserve [Line Items]
Initial Charge Recorded		0
Ending Reserve Balance		0
2020 Restructuring Plan | Operating Segments | Market Intelligence
Restructuring Cost and Reserve [Line Items]
Initial Charge Recorded		2
Ending Reserve Balance		1
2020 Restructuring Plan | Operating Segments | Platts
Restructuring Cost and Reserve [Line Items]
Initial Charge Recorded		0
Ending Reserve Balance		0
2020 Restructuring Plan | Corporate
Restructuring Cost and Reserve [Line Items]
Initial Charge Recorded		10
Ending Reserve Balance		6
2019 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Initial Charge Recorded		25
Ending Reserve Balance		5		$ 18
2019 Restructuring Plan | Operating Segments | Ratings
Restructuring Cost and Reserve [Line Items]
Initial Charge Recorded		11
Ending Reserve Balance		1
2019 Restructuring Plan | Operating Segments | Market Intelligence
Restructuring Cost and Reserve [Line Items]
Initial Charge Recorded		6
Ending Reserve Balance		2
2019 Restructuring Plan | Operating Segments | Platts
Restructuring Cost and Reserve [Line Items]
Initial Charge Recorded		1
Ending Reserve Balance		0
2019 Restructuring Plan | Corporate
Restructuring Cost and Reserve [Line Items]
Initial Charge Recorded		7
Ending Reserve Balance		$ 2