Earnings Per Share - Summary (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Amounts attributable to S&P Global Inc. common shareholders:
Net income	$ 555	$ 461	$ 965	$ 951
Basic weighted-average number of common shares outstanding (shares)	246.1	251.1	246.4	251.7
Effect of stock options and other dilutive securities (shares)	1.3	2.2	1.5	2.1
Diluted weighted-average number of common shares outstanding (shares)	247.4	253.3	247.9	253.8
Earnings per share attributable to S&P Global Inc. common shareholders:
Basic (USD per share)	$ 2.25	$ 1.83	$ 3.92	$ 3.78
Diluted (USD per share)	$ 2.24	$ 1.82	$ 3.89	$ 3.75