Restructuring (Details) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2017 USD ($)	Sep. 30, 2017 USD ($) position	Sep. 30, 2016 USD ($)	Dec. 31, 2016 USD ($)
Ratings
Restructuring Cost and Reserve [Line Items]
Employee termination charges	$ 15	$ 15	$ 6
Market and Commodities Intelligence
Restructuring Cost and Reserve [Line Items]
Employee termination charges		$ 5
2017 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Workforce reduction (in positions) | position		200
Employee termination charges		$ 24
Ending Reserve Balance	23	23
Reduction of reserve		1
2017 Restructuring Plan | Ratings
Restructuring Cost and Reserve [Line Items]
Initial Charge Recorded		15
Ending Reserve Balance	15	15
2017 Restructuring Plan | Market and Commodities Intelligence
Restructuring Cost and Reserve [Line Items]
Initial Charge Recorded		5
Ending Reserve Balance	4	4
2017 Restructuring Plan | Indices
Restructuring Cost and Reserve [Line Items]
Initial Charge Recorded		0
Ending Reserve Balance	0	0
2017 Restructuring Plan | Corporate
Restructuring Cost and Reserve [Line Items]
Initial Charge Recorded		4
Ending Reserve Balance	4	$ 4
2016 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Workforce reduction (in positions) | position		230
Initial Charge Recorded		$ 30
Ending Reserve Balance	12	12		$ 23
Restructuring charges paid		11
2016 Restructuring Plan | Ratings
Restructuring Cost and Reserve [Line Items]
Initial Charge Recorded		14
Ending Reserve Balance	4	4
2016 Restructuring Plan | Market and Commodities Intelligence
Restructuring Cost and Reserve [Line Items]
Initial Charge Recorded		10
Ending Reserve Balance	5	5
2016 Restructuring Plan | Indices
Restructuring Cost and Reserve [Line Items]
Initial Charge Recorded		1
Ending Reserve Balance	0	0
2016 Restructuring Plan | Corporate
Restructuring Cost and Reserve [Line Items]
Initial Charge Recorded		5
Ending Reserve Balance	$ 3	$ 3