Restructuring - Summary (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
2019 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Initial Charge Recorded		$ 20
Ending Reserve Balance		16
2018 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Initial Charge Recorded		25
Ending Reserve Balance		2		$ 24
Operating Segments | Ratings
Restructuring Cost and Reserve [Line Items]
Initial Charge Recorded		11
Operating Segments | Market Intelligence
Restructuring Cost and Reserve [Line Items]
Initial Charge Recorded		1
Operating Segments | Platts
Restructuring Cost and Reserve [Line Items]
Initial Charge Recorded		1
Operating Segments | 2019 Restructuring Plan | Ratings
Restructuring Cost and Reserve [Line Items]
Initial Charge Recorded		11
Ending Reserve Balance		9
Operating Segments | 2019 Restructuring Plan | Market Intelligence
Restructuring Cost and Reserve [Line Items]
Initial Charge Recorded		1
Ending Reserve Balance		1
Operating Segments | 2019 Restructuring Plan | Platts
Restructuring Cost and Reserve [Line Items]
Initial Charge Recorded		1
Ending Reserve Balance		0
Operating Segments | 2018 Restructuring Plan | Ratings
Restructuring Cost and Reserve [Line Items]
Initial Charge Recorded		8
Ending Reserve Balance		0
Operating Segments | 2018 Restructuring Plan | Market Intelligence
Restructuring Cost and Reserve [Line Items]
Initial Charge Recorded		7
Ending Reserve Balance		1
Operating Segments | 2018 Restructuring Plan | Platts
Restructuring Cost and Reserve [Line Items]
Initial Charge Recorded		0
Ending Reserve Balance		0
Corporate
Restructuring Cost and Reserve [Line Items]
Initial Charge Recorded	$ 7	7	$ 7
Corporate | 2019 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Initial Charge Recorded		7
Ending Reserve Balance		6
Corporate | 2018 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Initial Charge Recorded		10
Ending Reserve Balance		$ 1