Earnings Per Share - Summary (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Amounts attributable to S&P Global Inc. common shareholders:
Net income	$ 792	$ 555	$ 1,431	$ 965
Basic weighted-average number of common shares outstanding (shares)	240.9	246.1	241.5	246.4
Effect of stock options and other dilutive securities (shares)	1.0	1.3	1.1	1.5
Diluted weighted-average number of common shares outstanding (shares)	241.9	247.4	242.6	247.9
Earnings per share attributable to S&P Global Inc. common shareholders:
Basic (USD per share)	$ 3.29	$ 2.25	$ 5.92	$ 3.92
Diluted (USD per share)	$ 3.28	$ 2.24	$ 5.90	$ 3.89