Condensed Consolidating Financial Statements - Statement of Cash Flows (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating Activities:
Net income	$ 299	$ 452	$ 457	$ 430	$ 569	$ 923	$ 412	$ 323	$ 1,638	$ 2,228	$ 1,268
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation									82	85	90
Amortization of intangibles									98	96	67
Provision for losses on accounts receivable									16	9	8
Deferred income taxes									0	79	280
Stock-based compensation									99	76	78
Gain on dispositions									0	(1,101)	(11)
Accrued legal and regulatory settlements									55	54	119
Other									96	30	57
Changes in operating assets and liabilities, net of effect of acquisitions and dispositions:
Accounts receivable									(196)	(177)	(118)
Prepaid and other current assets									10	5	5
Accounts payable and accrued expenses									75	19	(9)
Unearned revenue									85	107	129
Accrued legal and regulatory settlements									(4)	(150)	(1,624)
Other current liabilities									(85)	(19)	(77)
Net change in prepaid/accrued income taxes									32	174	129
Net change in other assets and liabilities									15	45	(35)
Cash provided by operating activities from continuing operations									2,016	1,560	356
Investing Activities:
Capital expenditures									(123)	(115)	(139)
Acquisitions, net of cash acquired									(83)	(177)	(2,396)
Proceeds from dispositions									2	1,498	14
Changes in short-term investments									(5)	(1)	(4)
Cash (used for) provided by investing activities from continuing operations									(209)	1,205	(2,525)
Financing Activities:
(Payments on) / additions to short-term debt, net									0	(143)	143
Proceeds from issuance of senior notes, net									0	493	2,674
Payments on senior notes									0	(421)	0
Dividends paid to shareholders									(421)	(380)	(363)
Distributions to noncontrolling interest holders									(111)	(116)	(104)
Repurchase of treasury shares									(1,001)	(1,123)	(974)
Exercise of stock options									75	88	86
Contingent consideration payments									0	(39)	(5)
Purchase of additional CRISIL shares									0	0	(16)
Employee withholding tax on share-based payments									(49)	(55)	(92)
Intercompany financing activities									0	0	0
Cash (used for) provided by financing activities from continuing operations									(1,507)	(1,696)	1,349
Effect of exchange rate changes on cash									87	(158)	(67)
Cash provided by continuing operations									387	911	(887)
Discontinued Operations:
Cash used for operating activities									0	0	(129)
Cash used for discontinued operations									0	0	(129)
Net change in cash and cash equivalents									387	911	(1,016)
Cash and cash equivalents at beginning of year				2,392				1,481	2,392	1,481	2,497
Cash and cash equivalents at end of year	2,779				2,392				2,779	2,392	1,481
Eliminations
Operating Activities:
Net income									(5,983)	(3,374)	(1,745)
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 dispositions										0	0
Accrued legal and regulatory 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 and regulatory 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 from continuing operations									(5,983)	(3,374)	(1,745)
Investing Activities:
Capital expenditures									0	0	0
Acquisitions, net of cash acquired									0	0	0
Proceeds from dispositions									0	0	0
Changes in short-term investments									0	0	0
Cash (used for) provided by investing activities from continuing operations									0	0	0
Financing Activities:
(Payments on) / additions to short-term debt, net										0	0
Proceeds from issuance of senior notes, net										0	0
Payments on senior notes										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 payments										0	0
Purchase of additional CRISIL shares											0
Employee withholding tax on share-based payments									0	0	0
Intercompany financing activities									5,983	3,374	1,745
Cash (used for) provided by financing activities from continuing operations									5,983	3,374	1,745
Effect of exchange rate changes on cash									0	0	0
Cash provided by continuing operations											0
Discontinued Operations:
Cash used for operating activities											0
Cash used for discontinued operations											0
Net change in cash and cash equivalents									0	0	0
Cash and cash equivalents at beginning of year				0				0	0	0	0
Cash and cash equivalents at end of year	0				0				0	0	0
S&P Global Inc. | Reportable Legal Entities
Operating Activities:
Net income									3,670	3,069	1,449
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation									31	38	40
Amortization of intangibles									0	0	0
Provision for losses on accounts receivable									2	1	1
Deferred income taxes									108	16	33
Stock-based compensation									35	22	23
Gain on dispositions										(1,072)	0
Accrued legal and regulatory settlements									0	3	0
Other									34	48	23
Changes in operating assets and liabilities, net of effect of acquisitions and dispositions:
Accounts receivable									(2)	(24)	3
Prepaid and other current assets									(5)	(2)	(4)
Accounts payable and accrued expenses									22	(8)	8
Unearned revenue									19	19	(5)
Accrued legal and regulatory settlements									0	0	0
Other current liabilities									(42)	(27)	(31)
Net change in prepaid/accrued income taxes									41	141	14
Net change in other assets and liabilities									7	(9)	78
Cash provided by operating activities from continuing operations									3,920	2,215	1,632
Investing Activities:
Capital expenditures									(55)	(68)	(67)
Acquisitions, net of cash acquired									0	(144)	(2,243)
Proceeds from dispositions									0	1,422	0
Changes in short-term investments									0	0	0
Cash (used for) provided by investing activities from continuing operations									(55)	1,210	(2,310)
Financing Activities:
(Payments on) / additions to short-term debt, net										(143)	143
Proceeds from issuance of senior notes, net										493	2,674
Payments on senior notes										(421)
Dividends paid to shareholders									(421)	(380)	(363)
Distributions to noncontrolling interest holders									0	0	0
Repurchase of treasury shares									(1,001)	(1,123)	(974)
Exercise of stock options									68	86	80
Contingent consideration payments										(5)	(5)
Purchase of additional CRISIL shares											0
Employee withholding tax on share-based payments									(49)	(55)	(92)
Intercompany financing activities									(2,546)	(1,333)	(2,020)
Cash (used for) provided by financing activities from continuing operations									(3,949)	(2,881)	(557)
Effect of exchange rate changes on cash									5	0	0
Cash provided by continuing operations											(1,235)
Discontinued Operations:
Cash used for operating activities											0
Cash used for discontinued operations											0
Net change in cash and cash equivalents									(79)	544	(1,235)
Cash and cash equivalents at beginning of year				711				167	711	167	1,402
Cash and cash equivalents at end of year	632				711				632	711	167
Standard & Poor's Financial Services LLC | Reportable Legal Entities
Operating Activities:
Net income									649	767	824
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation									11	9	18
Amortization of intangibles									0	0	0
Provision for losses on accounts receivable									3	0	1
Deferred income taxes									(10)	(9)	290
Stock-based compensation									22	17	24
Gain on dispositions										0	0
Accrued legal and regulatory settlements									0	1	110
Other									19	5	16
Changes in operating assets and liabilities, net of effect of acquisitions and dispositions:
Accounts receivable									(23)	187	(27)
Prepaid and other current assets									3	10	14
Accounts payable and accrued expenses									97	(39)	(34)
Unearned revenue									2	(395)	66
Accrued legal and regulatory settlements									(1)	(108)	(1,624)
Other current liabilities									(12)	(27)	(35)
Net change in prepaid/accrued income taxes									(18)	0	0
Net change in other assets and liabilities									(6)	38	8
Cash provided by operating activities from continuing operations									736	456	(349)
Investing Activities:
Capital expenditures									(32)	(15)	(10)
Acquisitions, net of cash acquired									0	0	0
Proceeds from dispositions									0	0	0
Changes in short-term investments									0	0	0
Cash (used for) provided by investing activities from continuing operations									(32)	(15)	(10)
Financing Activities:
(Payments on) / additions to short-term debt, net										0	0
Proceeds from issuance of senior notes, net										0	0
Payments on senior notes										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 payments										0	0
Purchase of additional CRISIL shares											0
Employee withholding tax on share-based payments									0	0	0
Intercompany financing activities									(704)	(441)	359
Cash (used for) provided by financing activities from continuing operations									(704)	(441)	359
Effect of exchange rate changes on cash									0	0	0
Cash provided by continuing operations											0
Discontinued Operations:
Cash used for operating activities											0
Cash used for discontinued operations											0
Net change in cash and cash equivalents									0	0	0
Cash and cash equivalents at beginning of year				0				0	0	0	0
Cash and cash equivalents at end of year	0				0				0	0	0
Non-Guarantor Subsidiaries | Reportable Legal Entities
Operating Activities:
Net income									3,302	1,766	740
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation									40	38	32
Amortization of intangibles									98	96	67
Provision for losses on accounts receivable									11	8	6
Deferred income taxes									(98)	72	(43)
Stock-based compensation									42	37	31
Gain on dispositions										(29)	(11)
Accrued legal and regulatory settlements									55	50	9
Other									43	(23)	18
Changes in operating assets and liabilities, net of effect of acquisitions and dispositions:
Accounts receivable									(171)	(340)	(94)
Prepaid and other current assets									12	(3)	(5)
Accounts payable and accrued expenses									(44)	66	17
Unearned revenue									64	483	68
Accrued legal and regulatory settlements									(3)	(42)	0
Other current liabilities									(31)	35	(11)
Net change in prepaid/accrued income taxes									9	33	115
Net change in other assets and liabilities									14	16	(121)
Cash provided by operating activities from continuing operations									3,343	2,263	818
Investing Activities:
Capital expenditures									(36)	(32)	(62)
Acquisitions, net of cash acquired									(83)	(33)	(153)
Proceeds from dispositions									2	76	14
Changes in short-term investments									(5)	(1)	(4)
Cash (used for) provided by investing activities from continuing operations									(122)	10	(205)
Financing Activities:
(Payments on) / additions to short-term debt, net										0	0
Proceeds from issuance of senior notes, net										0	0
Payments on senior notes										0
Dividends paid to shareholders									0	0	0
Distributions to noncontrolling interest holders									(111)	(116)	(104)
Repurchase of treasury shares									0	0	0
Exercise of stock options									7	2	6
Contingent consideration payments										(34)	0
Purchase of additional CRISIL shares											(16)
Employee withholding tax on share-based payments									0	0	0
Intercompany financing activities									(2,733)	(1,600)	(84)
Cash (used for) provided by financing activities from continuing operations									(2,837)	(1,748)	(198)
Effect of exchange rate changes on cash									82	(158)	(67)
Cash provided by continuing operations											348
Discontinued Operations:
Cash used for operating activities											(129)
Cash used for discontinued operations											(129)
Net change in cash and cash equivalents									466	367	219
Cash and cash equivalents at beginning of year				$ 1,681				$ 1,314	1,681	1,314	1,095
Cash and cash equivalents at end of year	$ 2,147				$ 1,681				$ 2,147	$ 1,681	$ 1,314