Condensed Consolidating Financial Statements - Statement of Cash Flows (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Operating Activities:
Net income	$ 501	$ 457	$ 1,035	$ 887
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation			40	39
Amortization of intangibles			57	49
Provision for losses on accounts receivable			10	13
Stock-based compensation			46	41
Other			102	26
Changes in operating assets and liabilities, net of effect of acquisitions and dispositions:
Accounts receivable			19	(49)
Prepaid and other current assets			(19)	(13)
Accounts payable and accrued expenses			(217)	(139)
Unearned revenue			41	(17)
Accrued legal settlements			(29)	(4)
Other current liabilities			(69)	(85)
Net change in prepaid/accrued income taxes			24	(45)
Net change in other assets and liabilities			(137)	(29)
Cash provided by operating activities			903	674
Investing Activities:
Capital expenditures			(60)	(56)
Acquisitions, net of cash acquired			(246)	(70)
Proceeds from dispositions			0	2
Changes in short-term investments			1	0
Cash used for investing activities			(305)	(124)
Financing Activities:
Proceeds from issuance of senior notes, net			489	0
Payments on senior notes			(403)	0
Dividends paid to shareholders			(253)	(212)
Distributions to noncontrolling interest holders			(78)	(54)
Purchase of CRISIL shares			25	0
Repurchase of treasury shares			(1,100)	(346)
Exercise of stock options			16	38
Employee withholding tax on share-based payments			(50)	(44)
Intercompany financing activities			0	0
Cash used for financing activities			(1,404)	(618)
Effect of exchange rate changes on cash from continuing operations			(38)	60
Net change in cash, cash equivalents, and restricted cash			(844)	(8)
Cash, cash equivalents, and restricted cash at beginning of period			2,779	2,392
Cash, cash equivalents, and restricted cash at end of period	1,935	2,384	1,935	2,384
Eliminations
Operating Activities:
Net income	(1,106)	(1,719)	(3,635)	(3,780)
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation			0	0
Amortization of intangibles			0	0
Provision for losses on accounts receivable			0	0
Stock-based compensation			0	0
Other				0
Changes in operating assets and liabilities, net of effect of acquisitions and dispositions:
Accounts receivable			0	0
Prepaid and other current assets			0	0
Accounts payable and accrued expenses				0
Unearned revenue				0
Accrued legal settlements			0	0
Other current liabilities				0
Net change in prepaid/accrued income taxes			0	0
Net change in other assets and liabilities				0
Cash provided by operating activities			(3,635)	(3,780)
Investing Activities:
Capital expenditures			0	0
Acquisitions, net of cash acquired			0	0
Proceeds from dispositions				0
Changes in short-term investments			0
Cash used for investing activities			0	0
Financing Activities:
Proceeds from issuance of senior notes, net			0
Payments on senior notes			0
Dividends paid to shareholders			0	0
Distributions to noncontrolling interest holders			0	0
Purchase of CRISIL shares			0
Repurchase of treasury shares			0	0
Exercise of stock options			0	0
Employee withholding tax on share-based payments			0	0
Intercompany financing activities			3,635	3,780
Cash used for financing activities			3,635	3,780
Effect of exchange rate changes on cash from continuing operations			0	0
Net change in cash, cash equivalents, and restricted cash			0	0
Cash, cash equivalents, and restricted cash at beginning of period			0	0
Cash, cash equivalents, and restricted cash at end of period	0	0	0	0
S&P Global Inc.
Investing Activities:
Changes in short-term investments			0
S&P Global Inc. | Reportable Legal Entities
Operating Activities:
Net income	754	1,075	2,262	2,311
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation			15	15
Amortization of intangibles			0	0
Provision for losses on accounts receivable			0	0
Stock-based compensation			14	14
Other			(67)	17
Changes in operating assets and liabilities, net of effect of acquisitions and dispositions:
Accounts receivable			(6)	14
Prepaid and other current assets			(20)	(18)
Accounts payable and accrued expenses			(48)	(40)
Unearned revenue			9	1
Accrued legal settlements			(29)	0
Other current liabilities			20	(33)
Net change in prepaid/accrued income taxes			24	(55)
Net change in other assets and liabilities			(27)	(17)
Cash provided by operating activities			2,147	2,209
Investing Activities:
Capital expenditures			(43)	(19)
Acquisitions, net of cash acquired			0	0
Proceeds from dispositions				0
Cash used for investing activities			(43)	(19)
Financing Activities:
Proceeds from issuance of senior notes, net			489
Payments on senior notes			(403)
Dividends paid to shareholders			(253)	(212)
Distributions to noncontrolling interest holders			0	0
Purchase of CRISIL shares			0
Repurchase of treasury shares			(1,100)	(346)
Exercise of stock options			14	38
Employee withholding tax on share-based payments			(50)	(44)
Intercompany financing activities			(667)	(1,842)
Cash used for financing activities			(1,970)	(2,406)
Effect of exchange rate changes on cash from continuing operations			1	14
Net change in cash, cash equivalents, and restricted cash			135	(202)
Cash, cash equivalents, and restricted cash at beginning of period			632	711
Cash, cash equivalents, and restricted cash at end of period	767	509	767	509
Standard & Poor's Financial Services LLC
Investing Activities:
Changes in short-term investments			0
Standard & Poor's Financial Services LLC | Reportable Legal Entities
Operating Activities:
Net income	244	149	422	297
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation			4	5
Amortization of intangibles			0	0
Provision for losses on accounts receivable			1	4
Stock-based compensation			8	10
Other			0	0
Changes in operating assets and liabilities, net of effect of acquisitions and dispositions:
Accounts receivable			(29)	(63)
Prepaid and other current assets			1	3
Accounts payable and accrued expenses			(68)	34
Unearned revenue			30	28
Accrued legal settlements			0	(1)
Other current liabilities			(4)	(4)
Net change in prepaid/accrued income taxes			1	0
Net change in other assets and liabilities			2	1
Cash provided by operating activities			368	314
Investing Activities:
Capital expenditures			(10)	(10)
Acquisitions, net of cash acquired			0	0
Proceeds from dispositions				0
Cash used for investing activities			(10)	(10)
Financing Activities:
Proceeds from issuance of senior notes, net			0
Payments on senior notes			0
Dividends paid to shareholders			0	0
Distributions to noncontrolling interest holders			0	0
Purchase of CRISIL shares			0
Repurchase of treasury shares			0	0
Exercise of stock options			0	0
Employee withholding tax on share-based payments			0	0
Intercompany financing activities			(358)	(304)
Cash used for financing activities			(358)	(304)
Effect of exchange rate changes on cash from continuing operations			0	0
Net change in cash, cash equivalents, and restricted cash			0	0
Cash, cash equivalents, and restricted cash at beginning of period			0	0
Cash, cash equivalents, and restricted cash at end of period	0	0	0	0
Non-Guarantor Subsidiaries
Investing Activities:
Changes in short-term investments			1
Non-Guarantor Subsidiaries | Reportable Legal Entities
Operating Activities:
Net income	609	952	1,986	2,059
Adjustments to reconcile net income to cash provided by operating activities:
Depreciation			21	19
Amortization of intangibles			57	49
Provision for losses on accounts receivable			9	9
Stock-based compensation			24	17
Other			169	9
Changes in operating assets and liabilities, net of effect of acquisitions and dispositions:
Accounts receivable			54	0
Prepaid and other current assets			0	2
Accounts payable and accrued expenses			(101)	(133)
Unearned revenue			2	(46)
Accrued legal settlements			0	(3)
Other current liabilities			(85)	(48)
Net change in prepaid/accrued income taxes			(1)	10
Net change in other assets and liabilities			(112)	(13)
Cash provided by operating activities			2,023	1,931
Investing Activities:
Capital expenditures			(7)	(27)
Acquisitions, net of cash acquired			(246)	(70)
Proceeds from dispositions				2
Cash used for investing activities			(252)	(95)
Financing Activities:
Proceeds from issuance of senior notes, net			0
Payments on senior notes			0
Dividends paid to shareholders			0	0
Distributions to noncontrolling interest holders			(78)	(54)
Purchase of CRISIL shares			25
Repurchase of treasury shares			0	0
Exercise of stock options			2	0
Employee withholding tax on share-based payments			0	0
Intercompany financing activities			(2,610)	(1,634)
Cash used for financing activities			(2,711)	(1,688)
Effect of exchange rate changes on cash from continuing operations			(39)	46
Net change in cash, cash equivalents, and restricted cash			(979)	194
Cash, cash equivalents, and restricted cash at beginning of period			2,147	1,681
Cash, cash equivalents, and restricted cash at end of period	$ 1,168	$ 1,875	$ 1,168	$ 1,875