Consolidated Statements of Income - USD ($) shares in Millions, $ in Millions	3 Months Ended		12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement [Abstract]
Revenue	$ 1,589	$ 1,399	$ 6,063	$ 5,661	$ 5,313
Expenses:
Operating-related expenses			1,713	1,773	1,718
Selling and general expenses			1,560	1,439	1,532
Depreciation			82	85	90
Amortization of intangibles			98	96	67
Total expenses			3,453	3,393	3,407
Gain on dispositions			0	(1,101)	(11)
Operating profit	628	857	2,610	3,369	1,917
Interest expense, net			149	181	102
Income before taxes on income			2,461	3,188	1,815
Provision for taxes on income			823	960	547
Net income	299	569	1,638	2,228	1,268
Less: net income attributable to noncontrolling interests			(142)	(122)	(112)
Net income attributable to S&P Global Inc.	$ 263	$ 537	$ 1,496	$ 2,106	$ 1,156
Net income:
Basic (in dollars per share)	$ 1.03	$ 2.07	$ 5.84	$ 8.02	$ 4.26
Diluted (in dollars per share)	$ 1.02	$ 2.05	$ 5.78	$ 7.94	$ 4.21
Weighted-average number of common shares outstanding:
Basic (in shares)			256.3	262.8	271.6
Diluted (in shares)			258.9	265.2	274.6
Actual shares outstanding at year end (in shares)	253.7	258.3	253.7	258.3	265.2
Dividend declared per common share (in dollars per share)			$ 1.64	$ 1.44	$ 1.32