Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 534	$ 430
Other comprehensive income:
Foreign currency translation adjustment	23	30
Income tax effect	(18)	0
Foreign currency translation adjustment, net of income tax effect	5	30
Pension and other postretirement benefit plans	4	4
Income tax effect	(1)	(1)
Pension and other postretirement benefit plans, net of income tax effect	3	3
Unrealized gain on forward exchange contracts	1	7
Income tax effect	0	(2)
Unrealized gain on forward exchange contracts, net of income tax effect	1	5
Comprehensive income	543	468
Less: comprehensive income attributable to nonredeemable noncontrolling interests	(3)	(1)
Less: comprehensive income attributable to redeemable noncontrolling interests	(40)	(30)
Comprehensive income attributable to S&P Global Inc.	$ 500	$ 437