Quarterly Financial Information (Unaudited) - Summary (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Revenue	$ 1,867	$ 1,846	$ 1,943	$ 1,786	$ 1,735	$ 1,689	$ 1,704	$ 1,571	$ 7,442	$ 6,699	$ 6,258
Operating profit	656	944	1,105	912	818	891	813	705	3,617	3,226	2,790
Net income	505	498	842	689	585	662	602	453	2,534	2,303	2,121
Net income attributable to S&P Global common shareholders	$ 454	$ 455	$ 792	$ 639	$ 541	$ 617	$ 555	$ 410	$ 2,339	$ 2,123	$ 1,958
Net income:
Basic (USD per share)	$ 1.89	$ 1.89	$ 3.29	$ 2.64	$ 2.22	$ 2.52	$ 2.25	$ 1.66	$ 9.71	$ 8.65	$ 7.80
Diluted (USD per share)	$ 1.88	$ 1.88	$ 3.28	$ 2.62	$ 2.20	$ 2.50	$ 2.24	$ 1.65	$ 9.66	$ 8.60	$ 7.73