Condensed Consolidating Financial Statements - Statement of Income (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Condensed Income Statements, Captions [Line Items]
Revenue	$ 1,536	$ 1,546	$ 1,609	$ 1,567	$ 1,589	$ 1,513	$ 1,509	$ 1,453	$ 6,258	$ 6,063	$ 5,661
Expenses:
Operating-related expenses									1,701	1,695	1,773
Selling and general expenses									1,561	1,605	1,467
Depreciation									84	82	85
Amortization of intangibles									122	98	96
Total expenses									3,468	3,480	3,421
Gain on disposition									0	0	(1,101)
Operating profit	704	704	672	711	627	649	668	639	2,790	2,583	3,341
Other income, net									(25)	(27)	(28)
Interest expense (income), net									134	149	181
Non-operating intercompany transactions									0	0	0
Income before taxes on income									2,681	2,461	3,188
(Benefit) Provision for taxes on income									560	823	960
Equity in net income of subsidiaries									0	0	0
Net income	551	535	501	534	299	452	457	430	2,121	1,638	2,228
Less: net income attributable to noncontrolling interests									(163)	(142)	(122)
Net income attributable to S&P Global Inc.	$ 512	$ 495	$ 461	$ 491	$ 263	$ 414	$ 421	$ 399	1,958	1,496	2,106
Comprehensive income									2,018	1,762	2,055
Eliminations
Condensed Income Statements, Captions [Line Items]
Revenue									(153)	(138)	(126)
Expenses:
Operating-related expenses									(153)	(138)	(126)
Selling and general expenses									0	0	0
Depreciation									0	0	0
Amortization of intangibles									0	0	0
Total expenses									(153)	(138)	(126)
Gain on disposition											0
Operating profit									0	0	0
Other income, net									0	0	0
Interest expense (income), net									0	0	0
Non-operating intercompany transactions									1,584	2,175	668
Income before taxes on income									(1,584)	(2,175)	(668)
(Benefit) Provision for taxes on income									0	0	0
Equity in net income of subsidiaries									(3,575)	(3,808)	(2,706)
Net income									(5,159)	(5,983)	(3,374)
Less: net income attributable to noncontrolling interests									(163)	(142)	(122)
Net income attributable to S&P Global Inc.									(5,322)	(6,125)	(3,496)
Comprehensive income									(5,159)	(5,982)	(3,374)
S&P Global Inc. | Reportable Legal Entities
Condensed Income Statements, Captions [Line Items]
Revenue									776	717	667
Expenses:
Operating-related expenses									127	90	114
Selling and general expenses									183	196	128
Depreciation									37	31	38
Amortization of intangibles									0	0	0
Total expenses									347	317	280
Gain on disposition											(1,072)
Operating profit									429	400	1,459
Other income, net									(27)	(16)	(20)
Interest expense (income), net									143	163	191
Non-operating intercompany transactions									363	365	356
Income before taxes on income									(50)	(112)	932
(Benefit) Provision for taxes on income									(14)	26	275
Equity in net income of subsidiaries									3,576	3,808	2,412
Net income									3,540	3,670	3,069
Less: net income attributable to noncontrolling interests									0	0	0
Net income attributable to S&P Global Inc.									3,540	3,670	3,069
Comprehensive income									3,510	3,694	3,099
Standard & Poor's Financial Services LLC | Reportable Legal Entities
Condensed Income Statements, Captions [Line Items]
Revenue									1,695	1,780	1,513
Expenses:
Operating-related expenses									434	482	451
Selling and general expenses									292	345	243
Depreciation									7	11	9
Amortization of intangibles									0	0	0
Total expenses									733	838	703
Gain on disposition											0
Operating profit									962	942	810
Other income, net									0	0	0
Interest expense (income), net									2	0	0
Non-operating intercompany transactions									(75)	(77)	(83)
Income before taxes on income									1,035	1,019	893
(Benefit) Provision for taxes on income									250	370	420
Equity in net income of subsidiaries									(1)	0	294
Net income									784	649	767
Less: net income attributable to noncontrolling interests									0	0	0
Net income attributable to S&P Global Inc.									784	649	767
Comprehensive income									783	649	767
Non-Guarantor Subsidiaries | Reportable Legal Entities
Condensed Income Statements, Captions [Line Items]
Revenue									3,940	3,704	3,607
Expenses:
Operating-related expenses									1,293	1,261	1,334
Selling and general expenses									1,086	1,064	1,096
Depreciation									40	40	38
Amortization of intangibles									122	98	96
Total expenses									2,541	2,463	2,564
Gain on disposition											(29)
Operating profit									1,399	1,241	1,072
Other income, net									2	(11)	(8)
Interest expense (income), net									(11)	(14)	(10)
Non-operating intercompany transactions									(1,872)	(2,463)	(941)
Income before taxes on income									3,280	3,729	2,031
(Benefit) Provision for taxes on income									324	427	265
Equity in net income of subsidiaries									0	0	0
Net income									2,956	3,302	1,766
Less: net income attributable to noncontrolling interests									0	0	0
Net income attributable to S&P Global Inc.									2,956	3,302	1,766
Comprehensive income									$ 2,884	$ 3,401	$ 1,563