Segment and Geographic Information - Segment Information (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Segment information
Revenue	$ 1,399	$ 1,439	$ 1,482	$ 1,341	$ 1,374	$ 1,324	$ 1,342	$ 1,273	$ 5,661	$ 5,313	$ 5,051
Operating Profit (Loss)	857	1,348	$ 651	$ 512	424	$ 410	$ 582	$ 501	3,369	1,917	113
Amortization of intangibles									96	67	48
Pre-tax gain (loss) on dispositions	379	$ 722							1,100
Depreciation & Amortization									181	157	134
Capital Expenditures									115	139	92
Total Assets	8,669				8,183				8,669	8,183
Assets of a business held for sale	7				503				7	503
Operating segments
Segment information
Operating Profit (Loss)									3,496	2,055	282
Depreciation & Amortization									173	150	124
Capital Expenditures									102	130	84
Total Assets	5,963				5,812				5,963	5,812
Intersegment elimination
Segment information
Revenue									(98)	(88)	(86)
Segment reconciling items
Segment information
Operating Profit (Loss)									(127)	(138)	(169)
Restructuring costs										10	16
Pre-tax gain (loss) on dispositions									3	11
Corporate
Segment information
Depreciation & Amortization									8	7	10
Capital Expenditures									13	9	8
Total Assets	2,699				1,868				2,699	1,868
Ratings
Segment information
Total Assets	612				620				612	620
Ratings | Operating segments
Segment information
Revenue									2,535	2,428	2,455
Operating Profit (Loss)									1,262	1,078	(583)
Insurance Recoveries									10	54	1,600
Restructuring costs									6	13	45
Amortization of intangibles									5	5	6
Depreciation & Amortization									34	43	43
Capital Expenditures									42	48	33
Market and Commodities Intelligence
Segment information
Total Assets	4,104				4,011				4,104	4,011
Market and Commodities Intelligence | Operating segments
Segment information
Revenue									2,585	2,376	2,130
Operating Profit (Loss)									1,822	585	518
Restructuring costs										33	25
Amortization of intangibles									85	57	37
Impairment of intangible assets									24
Acquisition-related costs									1	37
Pre-tax gain (loss) on dispositions									1,100
Gain (loss) on write-down									(48)
Depreciation & Amortization									131	99	74
Capital Expenditures									57	78	49
Indices
Segment information
Total Assets	$ 1,247				$ 1,181				1,247	1,181
Indices | Operating segments
Segment information
Revenue									639	597	552
Operating Profit (Loss)									412	392	347
Amortization of intangibles									6	5	5
Legal fees											4
Depreciation & Amortization									8	8	7
Capital Expenditures									$ 3	$ 4	$ 2