Earnings Per Share - Summary (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Amounts attributable to S&P Global Inc. common shareholders:
Net income	$ 455	$ 617	$ 1,885	$ 1,582
Basic weighted-average number of common shares outstanding (shares)	240.6	245.0	241.2	245.9
Effect of stock options and other dilutive securities (shares)	1.0	1.5	1.1	1.5
Diluted weighted-average number of common shares outstanding (shares)	241.6	246.5	242.3	247.4
Earnings per share attributable to S&P Global Inc. common shareholders:
Basic (USD per share)	$ 1.89	$ 2.52	$ 7.82	$ 6.43
Diluted (USD per share)	$ 1.88	$ 2.50	$ 7.78	$ 6.40