Restructuring (Details) - 2016 Restructuring Plan $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($) position
Restructuring Cost and Reserve [Line Items]
Workforce reduction (in positions) | position		230
Initial Charge Recorded	$ 30
Ending Reserve Balance	17	$ 23
Restructuring charges paid	6
Ratings
Restructuring Cost and Reserve [Line Items]
Initial Charge Recorded	14
Ending Reserve Balance	8
Market and Commodities Intelligence
Restructuring Cost and Reserve [Line Items]
Initial Charge Recorded	10
Ending Reserve Balance	5
Indices
Restructuring Cost and Reserve [Line Items]
Initial Charge Recorded	1
Ending Reserve Balance	1
Corporate
Restructuring Cost and Reserve [Line Items]
Initial Charge Recorded	5
Ending Reserve Balance	$ 3