Quarterly Financial Information (Unaudited) - Summary (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Revenue	$ 1,735	$ 1,689	$ 1,704	$ 1,571	$ 1,536	$ 1,546	$ 1,609	$ 1,567	$ 6,699	$ 6,258	$ 6,063
Operating profit	818	891	813	705	704	704	672	711	3,226	2,790	2,583
Net income	585	662	602	453	551	535	501	534	2,303	2,121	1,638
Net income attributable to S&P Global common shareholders	$ 541	$ 617	$ 555	$ 410	$ 512	$ 495	$ 461	$ 491	$ 2,123	$ 1,958	$ 1,496
Net income:
Basic (USD per share)	$ 2.22	$ 2.52	$ 2.25	$ 1.66	$ 2.06	$ 1.97	$ 1.83	$ 1.94	$ 8.65	$ 7.80	$ 5.84
Diluted (USD per share)	$ 2.20	$ 2.50	$ 2.24	$ 1.65	$ 2.03	$ 1.95	$ 1.82	$ 1.93	$ 8.60	$ 7.73	$ 5.78