Condensed Consolidating Financial Statements - Statement of Income (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Condensed Income Statements, Captions [Line Items]
Revenue	$ 1,589	$ 1,513	$ 1,509	$ 1,453	$ 1,399	$ 1,439	$ 1,482	$ 1,341	$ 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	658	677	648	857	1,348	651	512	2,610	3,369	1,917
Interest expense (income), net									149	181	102
Non-operating intercompany transactions									0	0	0
Income before taxes on income									2,461	3,188	1,815
Provision for taxes on income									823	960	547
Equity in net income of subsidiaries									0	0	0
Net income	299	452	457	430	569	923	412	323	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	$ 414	$ 421	$ 399	$ 537	$ 892	$ 383	$ 294	1,496	2,106	1,156
Comprehensive income									1,762	2,055	1,182
Eliminations
Condensed Income Statements, Captions [Line Items]
Revenue									(138)	(126)	(115)
Expenses:
Operating-related expenses									(138)	(126)	(115)
Selling and general expenses									0	0	0
Depreciation									0	0	0
Amortization of intangibles									0	0	0
Total expenses									(138)	(126)	(115)
Gain on dispositions										0	0
Operating profit									0	0	0
Interest expense (income), net									0	0	0
Non-operating intercompany transactions									2,175	668	0
Income before taxes on income									(2,175)	(668)	0
Provision for taxes on income									0	0	0
Equity in net income of subsidiaries									(3,808)	(2,706)	(1,745)
Net income									(5,983)	(3,374)	(1,745)
Less: net income attributable to noncontrolling interests									(142)	(122)	(112)
Net income attributable to S&P Global Inc.									(6,125)	(3,496)	(1,857)
Comprehensive income									(5,982)	(3,374)	(1,741)
S&P Global Inc. | Reportable Legal Entities
Condensed Income Statements, Captions [Line Items]
Revenue									717	667	624
Expenses:
Operating-related expenses									108	113	137
Selling and general expenses									162	109	184
Depreciation									31	38	40
Amortization of intangibles									0	0	0
Total expenses									301	260	361
Gain on dispositions										(1,072)	0
Operating profit									416	1,479	263
Interest expense (income), net									163	191	112
Non-operating intercompany transactions									365	356	282
Income before taxes on income									(112)	932	(131)
Provision for taxes on income									26	275	(107)
Equity in net income of subsidiaries									3,808	2,412	1,473
Net income									3,670	3,069	1,449
Less: net income attributable to noncontrolling interests									0	0	0
Net income attributable to S&P Global Inc.									3,670	3,069	1,449
Comprehensive income									3,694	3,099	1,446
Standard & Poor's Financial Services LLC | Reportable Legal Entities
Condensed Income Statements, Captions [Line Items]
Revenue									1,780	1,513	2,141
Expenses:
Operating-related expenses									482	451	737
Selling and general expenses									345	243	254
Depreciation									11	9	18
Amortization of intangibles									0	0	0
Total expenses									838	703	1,009
Gain on dispositions										0	0
Operating profit									942	810	1,132
Interest expense (income), net									0	0	0
Non-operating intercompany transactions									(77)	(83)	222
Income before taxes on income									1,019	893	910
Provision for taxes on income									370	420	358
Equity in net income of subsidiaries									0	294	272
Net income									649	767	824
Less: net income attributable to noncontrolling interests									0	0	0
Net income attributable to S&P Global Inc.									649	767	824
Comprehensive income									649	767	822
Non-Guarantor Subsidiaries | Reportable Legal Entities
Condensed Income Statements, Captions [Line Items]
Revenue									3,704	3,607	2,663
Expenses:
Operating-related expenses									1,261	1,335	959
Selling and general expenses									1,053	1,087	1,094
Depreciation									40	38	32
Amortization of intangibles									98	96	67
Total expenses									2,452	2,556	2,152
Gain on dispositions										(29)	(11)
Operating profit									1,252	1,080	522
Interest expense (income), net									(14)	(10)	(10)
Non-operating intercompany transactions									(2,463)	(941)	(504)
Income before taxes on income									3,729	2,031	1,036
Provision for taxes on income									427	265	296
Equity in net income of subsidiaries									0	0	0
Net income									3,302	1,766	740
Less: net income attributable to noncontrolling interests									0	0	0
Net income attributable to S&P Global Inc.									3,302	1,766	740
Comprehensive income									$ 3,401	$ 1,563	$ 655