Condensed Consolidating Financial Statements - Statement of Income (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Condensed Income Statements, Captions [Line Items]
Revenue	$ 1,571	$ 1,567
Expenses:
Operating-related expenses	439	430
Selling and general expenses	375	381
Depreciation	20	21
Amortization of intangibles	32	24
Total expenses	866	856
Operating profit	705	711
Other expense (income), net	103	(4)
Interest expense (income), net	36	34
Non-operating intercompany transactions	0	0
Income before taxes on income	566	681
(Benefit) provision for taxes on income	113	147
Equity in net income of subsidiaries	0	0
Net income	453	534
Less: net income attributable to noncontrolling interests	(43)	(43)
Net income attributable to S&P Global Inc.	410	491
Comprehensive income	562	543
Eliminations
Condensed Income Statements, Captions [Line Items]
Revenue	(38)	(35)
Expenses:
Operating-related expenses	(38)	(35)
Selling and general expenses	0	0
Depreciation	0	0
Amortization of intangibles	0	0
Total expenses	(38)	(35)
Operating profit	0	0
Other expense (income), net	0	0
Interest expense (income), net	0	0
Non-operating intercompany transactions	23	1,016
Income before taxes on income	(23)	(1,016)
(Benefit) provision for taxes on income	0	0
Equity in net income of subsidiaries	(506)	(1,512)
Net income	(529)	(2,528)
Less: net income attributable to noncontrolling interests	(43)	(43)
Net income attributable to S&P Global Inc.	(572)	(2,571)
Comprehensive income	(530)	(2,533)
S&P Global Inc. | Reportable Legal Entities
Condensed Income Statements, Captions [Line Items]
Revenue	202	191
Expenses:
Operating-related expenses	33	25
Selling and general expenses	30	45
Depreciation	11	9
Amortization of intangibles	0	0
Total expenses	74	79
Operating profit	128	112
Other expense (income), net	107	(7)
Interest expense (income), net	38	38
Non-operating intercompany transactions	96	100
Income before taxes on income	(113)	(19)
(Benefit) provision for taxes on income	(40)	(14)
Equity in net income of subsidiaries	506	1,512
Net income	433	1,507
Less: net income attributable to noncontrolling interests	0	0
Net income attributable to S&P Global Inc.	433	1,507
Comprehensive income	515	1,487
Standard & Poor's Financial Services LLC | Reportable Legal Entities
Condensed Income Statements, Captions [Line Items]
Revenue	436	434
Expenses:
Operating-related expenses	117	117
Selling and general expenses	81	87
Depreciation	2	2
Amortization of intangibles	0	0
Total expenses	200	206
Operating profit	236	228
Other expense (income), net	0	0
Interest expense (income), net	0	0
Non-operating intercompany transactions	(16)	(20)
Income before taxes on income	252	248
(Benefit) provision for taxes on income	70	71
Equity in net income of subsidiaries	0	0
Net income	182	177
Less: net income attributable to noncontrolling interests	0	0
Net income attributable to S&P Global Inc.	182	177
Comprehensive income	182	177
Non-Guarantor Subsidiaries | Reportable Legal Entities
Condensed Income Statements, Captions [Line Items]
Revenue	971	977
Expenses:
Operating-related expenses	327	323
Selling and general expenses	264	249
Depreciation	7	10
Amortization of intangibles	32	24
Total expenses	630	606
Operating profit	341	371
Other expense (income), net	(4)	3
Interest expense (income), net	(2)	(4)
Non-operating intercompany transactions	(103)	(1,096)
Income before taxes on income	450	1,468
(Benefit) provision for taxes on income	83	90
Equity in net income of subsidiaries	0	0
Net income	367	1,378
Less: net income attributable to noncontrolling interests	0	0
Net income attributable to S&P Global Inc.	367	1,378
Comprehensive income	$ 395	$ 1,412