Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net income	$ 1,638	$ 2,228	$ 1,268
Other comprehensive income:
Foreign currency translation adjustment	93	(132)	(111)
Income tax effect	0	(7)	1
Foreign currency translation adjustment, net of income tax effect	93	(139)	(110)
Pension and other postretirement benefit plans	52	(27)	34
Income tax effect	(11)	(10)	(9)
Pension and other postretirement benefit plans, net of income tax effect	41	(37)	25
Unrealized loss on investment	(10)	0	0
Income tax effect	0	0	0
Unrealized loss on investment, net of income tax effect	(10)	0	0
Unrealized gain (loss) on forward exchange contracts	0	4	(1)
Income tax effect	0	(1)	0
Unrealized (loss) gain on investments and forward exchange contracts, net of income tax effect	0	3	(1)
Comprehensive income	1,762	2,055	1,182
Less: comprehensive income attributable to nonredeemable noncontrolling interests	(15)	(13)	(11)
Less: comprehensive income attributable to redeemable noncontrolling interests	(127)	(109)	(101)
Comprehensive income attributable to S&P Global Inc.	$ 1,620	$ 1,933	$ 1,070