Equity - Share Repurchases (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	1 Months Ended	3 Months Ended		9 Months Ended
	Oct. 31, 2018	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total number of shares purchased (shares)		2.0	0.7	5.4	5.7
Average price paid per share (USD per share)		$ 0	$ 205.11	$ 184.51	$ 180.94
Total cash utilized		$ 500	$ 13	$ 1,144	$ 1,113
Repurchase of treasury shares	$ 6			1,144	1,108
Total SPGI Equity
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total cash utilized		$ 500	$ 13	$ 1,144	$ 1,113