Earnings Per Share - Summary (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Amounts attributable to S&P Global Inc. common shareholders:
Net income		$ 455	$ 2,349	$ 1,885
Basic weighted-average number of common shares outstanding (shares)	240,900,000	240,600,000	240,800,000	241,200,000
Effect of stock options and other dilutive securities (shares)	800,000	1,000,000.0	900,000	1,100,000
Diluted weighted-average number of common shares outstanding (shares)	241,700,000	241,600,000	241,700,000	242,300,000
Earnings per share attributable to S&P Global Inc. common shareholders:
Basic (USD per share)	$ 3.31	$ 1.89	$ 9.76	$ 7.82
Diluted (USD per share)	$ 3.30	$ 1.88	$ 9.72	$ 7.78
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive shares excluded from computation of diluted earnings (shares)	0	0	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)			500,000	600,000