Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Amounts attributable to S&P Global Inc. common shareholders:
Net income	$ 399	$ 294
Basic weighted-average number of common shares outstanding (in shares)	258,200,000	265,000,000
Effect of stock options and other dilutive securities (in shares)	2,600,000	2,200,000
Diluted weighted-average number of common shares outstanding (in shares)	260,800,000	267,200,000
Earnings per share attributable to S&P Global Inc. common shareholders:
Basic (in dollars per share)	$ 1.54	$ 1.11
Diluted (in dollars per share)	$ 1.53	$ 1.10
Employee stock option
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Outstanding shares not included in the computation of diluted earnings per share (in shares)	0
Restricted performance shares
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Outstanding shares not included in the computation of diluted earnings per share (in shares)	700,000	900,000