Consolidated Statements of Equity - USD ($) $ in Millions		Total		Total SPGI Equity		Common Stock $1 par	Additional Paid-in Capital	Retained Income		Accumulated Other Comprehensive Loss		Less: Treasury Stock	Noncontrolling Interests
Balance at beginning of period at Dec. 31, 2018		$ 684		$ 628		$ 294	$ 833	$ 11,284		$ (742)		$ (11,041)	$ 56
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income		1,062	[1]	1,056	[1]			965		91			6
Dividends		(287)		(281)				(281)					(6)
Share repurchases		(644)		(644)								644
Employee stock plans		11		11			(43)					(54)
Capital contribution from noncontrolling interest		(36)		(36)				(36)
Change in redemption value of redeemable noncontrolling interest		(222)		(222)				(222)
Other		2		0									2
Balance at end of period at Jun. 30, 2019		$ 570		512		294	790	11,710		(651)		(11,631)	58
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends declared per common share (USD per share)		$ 1.14
Balance at beginning of period at Mar. 31, 2019		$ 388		327		294	772	11,532		(633)		(11,638)	61
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income	[1]	540		537				555		(18)			3
Dividends		(146)		(140)				(140)					(6)
Employee stock plans		25		25			18					(7)
Change in redemption value of redeemable noncontrolling interest		(237)		(237)				(237)
Balance at end of period at Jun. 30, 2019		$ 570		512		294	790	11,710		(651)		(11,631)	58
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends declared per common share (USD per share)		$ 0.57
Balance at beginning of period at Dec. 31, 2019		$ 536		479		294	903	12,205		(624)		(12,299)	57
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income		1,356	[1]	1,351	[1]			1,431	[1]	(80)	[1]		5
Dividends		(325)		(323)				(323)					(2)
Share repurchases		(1,153)		(1,153)			(120)					1,033
Employee stock plans		(20)		(20)			(21)					(1)
Change in redemption value of redeemable noncontrolling interest		(124)		(124)				(124)
Other		(2)		0									(2)
Balance at end of period at Jun. 30, 2020		$ 268		210		294	762	13,189		(704)		(13,331)	58
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends declared per common share (USD per share)		$ 1.34
Balance at beginning of period at Mar. 31, 2020		$ (194)		(250)		294	754	12,691		(660)		(13,329)	56
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income		752	[1]	748	[1]			792		(44)			4
Dividends		(164)		(162)				(162)					(2)
Employee stock plans		6		6			8					2
Change in redemption value of redeemable noncontrolling interest		(135)		(135)				(135)
Other		3		3				3
Balance at end of period at Jun. 30, 2020		$ 268		$ 210		$ 294	$ 762	$ 13,189		$ (704)		$ (13,331)	$ 58
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends declared per common share (USD per share)		$ 0.67

[1] Excludes comprehensive income of $46 million and $44 million for the three months ended June 30, 2020 and 2019, respectively, and $95 million and $84 million for the six months ended June 30, 2020 and 2019, respectively, attributable to our redeemable noncontrolling interest.