Earnings Per Share - Summary (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Amounts attributable to S&P Global Inc. common shareholders:
Net income	$ 617	$ 495	$ 1,582	$ 1,447
Basic weighted-average number of common shares outstanding (shares)	245.0	251.3	245.9	251.6
Effect of stock options and other dilutive securities (shares)	1.5	2.2	1.5	2.1
Diluted weighted-average number of common shares outstanding (shares)	246.5	253.5	247.4	253.7
Earnings per share attributable to S&P Global Inc. common shareholders:
Basic (USD per share)	$ 2.52	$ 1.97	$ 6.43	$ 5.75
Diluted (USD per share)	$ 2.50	$ 1.95	$ 6.40	$ 5.70