Condensed Consolidating Financial Statements - Statement of Income (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Condensed Income Statements, Captions [Line Items]
Revenue	$ 1,567	$ 1,453
Expenses:
Operating-related expenses	439	411
Selling and general expenses	372	360
Depreciation	21	19
Amortization of intangibles	24	24
Total expenses	856	814
Operating profit	711	639
Other (income) expense, net	(4)	(9)
Interest expense (income), net	34	37
Non-operating intercompany transactions	0	0
Income before taxes on income	681	611
(Benefit) provision for taxes on income	147	181
Equity in net income of subsidiaries	0	0
Net income	534	430
Less: net income attributable to noncontrolling interests	(43)	(31)
Net income attributable to S&P Global Inc.	491	399
Comprehensive income	543	468
Eliminations
Condensed Income Statements, Captions [Line Items]
Revenue	(35)	(32)
Expenses:
Operating-related expenses	(35)	(32)
Selling and general expenses	0	0
Depreciation	0	0
Amortization of intangibles	0	0
Total expenses	(35)	(32)
Operating profit	0	0
Other (income) expense, net	0	0
Interest expense (income), net	0	0
Non-operating intercompany transactions	1,016	838
Income before taxes on income	(1,016)	(838)
(Benefit) provision for taxes on income	0	0
Equity in net income of subsidiaries	(1,512)	(1,224)
Net income	(2,528)	(2,062)
Less: net income attributable to noncontrolling interests	(43)	(31)
Net income attributable to S&P Global Inc.	(2,571)	(2,093)
Comprehensive income	(2,533)	(2,064)
S&P Global Inc. | Reportable Legal Entities
Condensed Income Statements, Captions [Line Items]
Revenue	191	180
Expenses:
Operating-related expenses	34	31
Selling and general expenses	37	26
Depreciation	8	7
Amortization of intangibles	0	0
Total expenses	79	64
Operating profit	112	116
Other (income) expense, net	(7)	(6)
Interest expense (income), net	38	39
Non-operating intercompany transactions	100	82
Income before taxes on income	(19)	1
(Benefit) provision for taxes on income	(14)	(11)
Equity in net income of subsidiaries	1,512	1,224
Net income	1,507	1,236
Less: net income attributable to noncontrolling interests	0	0
Net income attributable to S&P Global Inc.	1,507	1,236
Comprehensive income	1,487	1,238
Standard & Poor's Financial Services LLC | Reportable Legal Entities
Condensed Income Statements, Captions [Line Items]
Revenue	434	438
Expenses:
Operating-related expenses	117	119
Selling and general expenses	87	88
Depreciation	2	3
Amortization of intangibles	0	0
Total expenses	206	210
Operating profit	228	228
Other (income) expense, net	0	0
Interest expense (income), net	0	0
Non-operating intercompany transactions	(20)	(19)
Income before taxes on income	248	247
(Benefit) provision for taxes on income	71	99
Equity in net income of subsidiaries	0	0
Net income	177	148
Less: net income attributable to noncontrolling interests	0	0
Net income attributable to S&P Global Inc.	177	148
Comprehensive income	177	147
Non-Guarantor Subsidiaries | Reportable Legal Entities
Condensed Income Statements, Captions [Line Items]
Revenue	977	867
Expenses:
Operating-related expenses	323	293
Selling and general expenses	248	246
Depreciation	11	9
Amortization of intangibles	24	24
Total expenses	606	572
Operating profit	371	295
Other (income) expense, net	3	(3)
Interest expense (income), net	(4)	(2)
Non-operating intercompany transactions	(1,096)	(901)
Income before taxes on income	1,468	1,201
(Benefit) provision for taxes on income	90	93
Equity in net income of subsidiaries	0	0
Net income	1,378	1,108
Less: net income attributable to noncontrolling interests	0	0
Net income attributable to S&P Global Inc.	1,378	1,108
Comprehensive income	$ 1,412	$ 1,147