Condensed Consolidating Financial Statements - Statement of Income (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Condensed Income Statements, Captions [Line Items]
Revenue	$ 1,609	$ 1,509	$ 3,176	$ 2,962
Expenses:
Operating-related expenses	446	432	884	843
Selling and general expenses	439	364	812	725
Depreciation	19	20	40	39
Amortization of intangibles	33	25	57	49
Total expenses	937	841	1,793	1,656
Operating profit	672	668	1,383	1,306
Other income, net	(11)	(9)	(16)	(18)
Interest expense (income), net	26	37	61	74
Non-operating intercompany transactions	0	0	0	0
Income before taxes on income	657	640	1,338	1,250
(Benefit) provision for taxes on income	156	183	303	363
Equity in net income of subsidiaries	0	0	0	0
Net income	501	457	1,035	887
Less: net income attributable to noncontrolling interests	(40)	(36)	(84)	(67)
Net income attributable to S&P Global Inc.	461	421	951	820
Comprehensive income	426	493	969	961
Eliminations
Condensed Income Statements, Captions [Line Items]
Revenue	(39)	(35)	(74)	(67)
Expenses:
Operating-related expenses	(39)	(35)	(74)	(67)
Selling and general expenses	0	0	0	0
Depreciation	0	0	0	0
Amortization of intangibles	0	0	0	0
Total expenses	(39)	(35)	(74)	(67)
Operating profit	0	0	0	0
Other income, net	0	0	0	0
Interest expense (income), net	0	0	0	0
Non-operating intercompany transactions	294	655	1,311	1,492
Income before taxes on income	(294)	(655)	(1,311)	(1,492)
(Benefit) provision for taxes on income	0	0	0	0
Equity in net income of subsidiaries	(812)	(1,064)	(2,324)	(2,288)
Net income	(1,106)	(1,719)	(3,635)	(3,780)
Less: net income attributable to noncontrolling interests	(40)	(36)	(84)	(67)
Net income attributable to S&P Global Inc.	(1,146)	(1,755)	(3,719)	(3,847)
Comprehensive income	(1,103)	(1,712)	(3,635)	(3,776)
S&P Global Inc. | Reportable Legal Entities
Condensed Income Statements, Captions [Line Items]
Revenue	200	181	391	361
Expenses:
Operating-related expenses	48	22	81	52
Selling and general expenses	70	49	108	76
Depreciation	7	8	15	15
Amortization of intangibles	0	0	0	0
Total expenses	125	79	204	143
Operating profit	75	102	187	218
Other income, net	(8)	(6)	(16)	(12)
Interest expense (income), net	28	40	66	79
Non-operating intercompany transactions	86	93	186	175
Income before taxes on income	(31)	(25)	(49)	(24)
(Benefit) provision for taxes on income	27	(36)	13	(47)
Equity in net income of subsidiaries	812	1,064	2,324	2,288
Net income	754	1,075	2,262	2,311
Less: net income attributable to noncontrolling interests	0	0	0	0
Net income attributable to S&P Global Inc.	754	1,075	2,262	2,311
Comprehensive income	764	1,085	2,251	2,323
Standard & Poor's Financial Services LLC | Reportable Legal Entities
Condensed Income Statements, Captions [Line Items]
Revenue	463	447	897	885
Expenses:
Operating-related expenses	107	115	224	234
Selling and general expenses	57	83	143	172
Depreciation	2	3	4	5
Amortization of intangibles	0	0	0	0
Total expenses	166	201	371	411
Operating profit	297	246	526	474
Other income, net	0	0	0	0
Interest expense (income), net	0	0	1	0
Non-operating intercompany transactions	(22)	(22)	(43)	(41)
Income before taxes on income	319	268	568	515
(Benefit) provision for taxes on income	75	119	146	218
Equity in net income of subsidiaries	0	0	0	0
Net income	244	149	422	297
Less: net income attributable to noncontrolling interests	0	0	0	0
Net income attributable to S&P Global Inc.	244	149	422	297
Comprehensive income	244	148	421	296
Non-Guarantor Subsidiaries | Reportable Legal Entities
Condensed Income Statements, Captions [Line Items]
Revenue	985	916	1,962	1,783
Expenses:
Operating-related expenses	330	330	653	624
Selling and general expenses	312	232	561	477
Depreciation	10	9	21	19
Amortization of intangibles	33	25	57	49
Total expenses	685	596	1,292	1,169
Operating profit	300	320	670	614
Other income, net	(3)	(3)	0	(6)
Interest expense (income), net	(2)	(3)	(6)	(5)
Non-operating intercompany transactions	(358)	(726)	(1,454)	(1,626)
Income before taxes on income	663	1,052	2,130	2,251
(Benefit) provision for taxes on income	54	100	144	192
Equity in net income of subsidiaries	0	0	0	0
Net income	609	952	1,986	2,059
Less: net income attributable to noncontrolling interests	0	0	0	0
Net income attributable to S&P Global Inc.	609	952	1,986	2,059
Comprehensive income	$ 521	$ 972	$ 1,932	$ 2,118