Earnings Per Share - Summary (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Amounts attributable to S&P Global Inc. common shareholders:
Net income	$ 410	$ 491
Basic weighted-average number of common shares outstanding (shares)	246.7	252.4
Effect of stock options and other dilutive securities (shares)	1.6	2.0
Diluted weighted-average number of common shares outstanding (shares)	248.3	254.4
Earnings per share attributable to S&P Global Inc. common shareholders:
Basic (USD per share)	$ 1.66	$ 1.94
Diluted (USD per share)	$ 1.65	$ 1.93