Condensed Consolidating Financial Statements - Statement of Cash Flows (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
Operating Activities:
Net income	$ 551	$ 535	$ 501	$ 534	$ 299	$ 452	$ 457	$ 430	$ 2,121	$ 1,638	$ 2,228
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation									84	82	85
Amortization of intangibles									122	98	96
Provision for losses on accounts receivable									21	16	9
Deferred income taxes									81	0	79
Stock-based compensation									94	99	76
Gain on disposition									0	0	(1,101)
Accrued legal settlements									1	55	54
Other									52	96	30
Changes in operating assets and liabilities, net of effect of acquisitions and dispositions:
Accounts receivable									(164)	(196)	(177)
Prepaid and other current assets									(1)	10	5
Accounts payable and accrued expenses									(106)	75	19
Unearned revenue									70	85	107
Accrued legal settlements									(108)	(4)	(150)
Other current liabilities									(67)	(85)	(19)
Net change in prepaid/accrued income taxes									(7)	32	174
Net change in other assets and liabilities									(129)	15	45
Cash provided by operating activities									2,064	2,016	1,560
Investing Activities:
Capital expenditures									(113)	(123)	(115)
Acquisitions, net of cash acquired									(401)	(83)	(177)
Contingent consideration payment									0	0	(34)
Proceeds from dispositions									6	2	1,498
Changes in short-term investments									(5)	(5)	(1)
Cash (used for) provided by investing activities									(513)	(209)	1,171
Financing Activities:
(Payments on) / additions to short-term debt, net									0	0	(143)
Proceeds from issuance of senior notes, net									489	0	493
Payments on senior notes									(403)	0	(421)
Dividends paid to shareholders									(503)	(421)	(380)
Distributions to noncontrolling interest holders									(154)	(111)	(116)
Repurchase of treasury shares									(1,660)	(1,001)	(1,123)
Exercise of stock options									34	75	88
Contingent consideration payment									0	0	(5)
Purchase of additional CRISIL shares									(25)	0	0
Employee withholding tax on share-based payments									(66)	(49)	(55)
Intercompany financing activities									0	0	0
Cash used for financing activities									(2,288)	(1,507)	(1,662)
Effect of exchange rate changes on cash									(84)	87	(158)
Net change in cash, cash equivalents, and restricted cash									(821)	387	911
Cash, cash equivalents, and restricted cash at beginning of year				2,779				2,392	2,779	2,392	1,481
Cash, cash equivalents, and restricted cash at end of year	1,958				2,779				1,958	2,779	2,392
Eliminations
Operating Activities:
Net income									(5,159)	(5,983)	(3,374)
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation									0	0	0
Amortization of intangibles									0	0	0
Provision for losses on accounts receivable									0	0	0
Deferred income taxes									0	0	0
Stock-based compensation									0	0	0
Gain on disposition											0
Accrued legal settlements									0	0	0
Other									0	0	0
Changes in operating assets and liabilities, net of effect of acquisitions and dispositions:
Accounts receivable									0	0	0
Prepaid and other current assets									0	0	0
Accounts payable and accrued expenses									0	0	0
Unearned revenue									0	0	0
Accrued legal settlements									0	0	0
Other current liabilities									0	0	0
Net change in prepaid/accrued income taxes									0	0	0
Net change in other assets and liabilities									0	0	0
Cash provided by operating activities									(5,159)	(5,983)	(3,374)
Investing Activities:
Capital expenditures									0	0	0
Acquisitions, net of cash acquired									0	0	0
Contingent consideration payment											0
Proceeds from dispositions									0	0	0
Changes in short-term investments									0	0	0
Cash (used for) provided by investing activities									0	0	0
Financing Activities:
(Payments on) / additions to short-term debt, net											0
Proceeds from issuance of senior notes, net									0		0
Payments on senior notes									0		0
Dividends paid to shareholders									0	0	0
Distributions to noncontrolling interest holders									0	0	0
Repurchase of treasury shares									0	0	0
Exercise of stock options									0	0	0
Contingent consideration payment											0
Purchase of additional CRISIL shares									0
Employee withholding tax on share-based payments									0	0	0
Intercompany financing activities									5,159	5,983	3,374
Cash used for financing activities									5,159	5,983	3,374
Effect of exchange rate changes on cash									0	0	0
Net change in cash, cash equivalents, and restricted cash									0	0	0
Cash, cash equivalents, and restricted cash at beginning of year				0				0	0	0	0
Cash, cash equivalents, and restricted cash at end of year	0				0				0	0	0
S&P Global Inc. | Reportable Legal Entities
Operating Activities:
Net income									3,540	3,670	3,069
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation									37	31	38
Amortization of intangibles									0	0	0
Provision for losses on accounts receivable									3	2	1
Deferred income taxes									33	108	16
Stock-based compensation									28	35	22
Gain on disposition											(1,072)
Accrued legal settlements									0	0	3
Other									46	34	48
Changes in operating assets and liabilities, net of effect of acquisitions and dispositions:
Accounts receivable									(27)	(2)	(24)
Prepaid and other current assets									(2)	(5)	(2)
Accounts payable and accrued expenses									(11)	22	(8)
Unearned revenue									(53)	19	19
Accrued legal settlements									0	0	0
Other current liabilities									(22)	(42)	(27)
Net change in prepaid/accrued income taxes									2	41	141
Net change in other assets and liabilities									(128)	7	(9)
Cash provided by operating activities									3,446	3,920	2,215
Investing Activities:
Capital expenditures									(81)	(55)	(68)
Acquisitions, net of cash acquired									0	0	(144)
Contingent consideration payment											0
Proceeds from dispositions									0	0	1,422
Changes in short-term investments									0	0	0
Cash (used for) provided by investing activities									(81)	(55)	1,210
Financing Activities:
(Payments on) / additions to short-term debt, net											(143)
Proceeds from issuance of senior notes, net									489		493
Payments on senior notes									(403)		(421)
Dividends paid to shareholders									(503)	(421)	(380)
Distributions to noncontrolling interest holders									0	0	0
Repurchase of treasury shares									(1,660)	(1,001)	(1,123)
Exercise of stock options									26	68	86
Contingent consideration payment											(5)
Purchase of additional CRISIL shares
Employee withholding tax on share-based payments									(66)	(49)	(55)
Intercompany financing activities									(1,181)	(2,546)	(1,333)
Cash used for financing activities									(3,298)	(3,949)	(2,881)
Effect of exchange rate changes on cash									(5)	5	0
Net change in cash, cash equivalents, and restricted cash									62	(79)	544
Cash, cash equivalents, and restricted cash at beginning of year				632				711	632	711	167
Cash, cash equivalents, and restricted cash at end of year	694				632				694	632	711
Standard & Poor's Financial Services LLC | Reportable Legal Entities
Operating Activities:
Net income									784	649	767
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation									7	11	9
Amortization of intangibles									0	0	0
Provision for losses on accounts receivable									4	3	0
Deferred income taxes									10	(10)	(9)
Stock-based compensation									16	22	17
Gain on disposition											0
Accrued legal settlements									1	0	1
Other									5	19	5
Changes in operating assets and liabilities, net of effect of acquisitions and dispositions:
Accounts receivable									39	(23)	187
Prepaid and other current assets									(4)	3	10
Accounts payable and accrued expenses									(64)	97	(39)
Unearned revenue									13	2	(395)
Accrued legal settlements									0	(1)	(108)
Other current liabilities									(11)	(12)	(27)
Net change in prepaid/accrued income taxes									0	(18)	0
Net change in other assets and liabilities									32	(6)	38
Cash provided by operating activities									832	736	456
Investing Activities:
Capital expenditures									(16)	(32)	(15)
Acquisitions, net of cash acquired									0	0	0
Contingent consideration payment											0
Proceeds from dispositions									0	0	0
Changes in short-term investments									0	0	0
Cash (used for) provided by investing activities									(16)	(32)	(15)
Financing Activities:
(Payments on) / additions to short-term debt, net											0
Proceeds from issuance of senior notes, net									0		0
Payments on senior notes									0		0
Dividends paid to shareholders									0	0	0
Distributions to noncontrolling interest holders									0	0	0
Repurchase of treasury shares									0	0	0
Exercise of stock options									0	0	0
Contingent consideration payment											0
Purchase of additional CRISIL shares									0
Employee withholding tax on share-based payments									0	0	0
Intercompany financing activities									(816)	(704)	(441)
Cash used for financing activities									(816)	(704)	(441)
Effect of exchange rate changes on cash									0	0	0
Net change in cash, cash equivalents, and restricted cash									0	0	0
Cash, cash equivalents, and restricted cash at beginning of year				$ 0				$ 0	0	0	0
Cash, cash equivalents, and restricted cash at end of year	$ 0				$ 0				$ 0	$ 0	$ 0