Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Amounts attributable to S&P Global Inc. common shareholders:
Net income	$ 892	$ 252	$ 1,569	$ 909
Basic weighted-average number of common shares outstanding (in shares)	262.9	271.3	264.1	272.6
Effect of stock options and other dilutive securities (in shares)	2.4	3.1	2.3	2.8
Diluted weighted-average number of common shares outstanding (in shares)	265.3	274.4	266.4	275.4
Earnings per share attributable to S&P Global Inc. common shareholders:
Basic (in dollars per share)	$ 3.39	$ 0.93	$ 5.94	$ 3.33
Diluted (in dollars per share)	$ 3.36	$ 0.92	$ 5.89	$ 3.30
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)			0.7	0.9