Equity (Schedule of stock repurchases) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	1 Months Ended	3 Months Ended
	Dec. 31, 2015	Mar. 31, 2017	Mar. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total number of shares purchased (in shares)	0.3	1.5	2.2
Average price paid per share (in dollars per share)		$ 129.97	$ 91.98
Total cash utilized	$ 26	$ 201
Cash used to repurchase shares		201	$ 226
Stock Repurchases
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Cash used to repurchase shares			226
Total SPGI Equity
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total cash utilized		$ 201	$ 200