Earnings Per Share - Summary (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Amounts attributable to S&P Global Inc. common shareholders:
Net income	$ 755	$ 639
Basic weighted-average number of common shares outstanding (shares)	240,600,000	242,100,000
Effect of stock options and other dilutive securities (shares)	1,000,000.0	1,200,000
Diluted weighted-average number of common shares outstanding (shares)	241,600,000	243,300,000
Earnings per share attributable to S&P Global Inc. common shareholders:
Basic (USD per share)	$ 3.14	$ 2.64
Diluted (USD per share)	$ 3.12	$ 2.62
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive shares excluded from computation of diluted earnings (shares)	0	0
Restricted performance shares
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive shares excluded from computation of diluted earnings (shares)	400,000	400,000