Earnings Per Share - Summary (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Amounts attributable to S&P Global Inc. common shareholders:
Net income		$ 792	$ 1,553	$ 1,431
Basic weighted-average number of common shares outstanding (shares)	240,800,000	240,900,000	240,700,000	241,500,000
Effect of stock options and other dilutive securities (shares)	1,000,000.0	1,000,000.0	1,000,000.0	1,100,000
Diluted weighted-average number of common shares outstanding (shares)	241,800,000	241,900,000	241,700,000	242,600,000
Earnings per share attributable to S&P Global Inc. common shareholders:
Basic (USD per share)	$ 3.31	$ 3.29	$ 6.45	$ 5.92
Diluted (USD per share)	$ 3.30	$ 3.28	$ 6.42	$ 5.90
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