Restructuring - Summary (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Restructuring Plan, 2018
Restructuring Cost and Reserve [Line Items]
Initial Charge Recorded	$ 25
Ending Reserve Balance	24
Restructuring Plan, 2017
Restructuring Cost and Reserve [Line Items]
Initial Charge Recorded		$ 44
Ending Reserve Balance	10
Ratings
Restructuring Cost and Reserve [Line Items]
Initial Charge Recorded	8	25	$ 6
Market Intelligence
Restructuring Cost and Reserve [Line Items]
Initial Charge Recorded		7
Platts
Restructuring Cost and Reserve [Line Items]
Initial Charge Recorded		2
Operating segments | Ratings | Restructuring Plan, 2018
Restructuring Cost and Reserve [Line Items]
Initial Charge Recorded	8
Ending Reserve Balance	8
Operating segments | Ratings | Restructuring Plan, 2017
Restructuring Cost and Reserve [Line Items]
Initial Charge Recorded		25
Ending Reserve Balance	7
Operating segments | Market Intelligence | Restructuring Plan, 2018
Restructuring Cost and Reserve [Line Items]
Initial Charge Recorded	7
Ending Reserve Balance	7
Operating segments | Market Intelligence | Restructuring Plan, 2017
Restructuring Cost and Reserve [Line Items]
Initial Charge Recorded		8
Ending Reserve Balance	1
Operating segments | Platts | Restructuring Plan, 2018
Restructuring Cost and Reserve [Line Items]
Initial Charge Recorded	0
Ending Reserve Balance	0
Operating segments | Platts | Restructuring Plan, 2017
Restructuring Cost and Reserve [Line Items]
Initial Charge Recorded		1
Ending Reserve Balance	0
Operating segments | Indices | Restructuring Plan, 2018
Restructuring Cost and Reserve [Line Items]
Initial Charge Recorded	0
Ending Reserve Balance	0
Operating segments | Indices | Restructuring Plan, 2017
Restructuring Cost and Reserve [Line Items]
Initial Charge Recorded		0
Ending Reserve Balance	0
Corporate
Restructuring Cost and Reserve [Line Items]
Initial Charge Recorded	10	10
Corporate | Restructuring Plan, 2018
Restructuring Cost and Reserve [Line Items]
Initial Charge Recorded	10
Ending Reserve Balance	9
Corporate | Restructuring Plan, 2017
Restructuring Cost and Reserve [Line Items]
Initial Charge Recorded		$ 10
Ending Reserve Balance	$ 2