Quarterly Financial Information (Unaudited) - Summary (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Revenue	$ 1,536	$ 1,546	$ 1,609	$ 1,567	$ 1,589	$ 1,513	$ 1,509	$ 1,453	$ 6,258	$ 6,063	$ 5,661
Operating profit	704	704	672	711	627	649	668	639	2,790	2,583	3,341
Net income	551	535	501	534	299	452	457	430	2,121	1,638	2,228
Net income attributable to S&P Global common shareholders	$ 512	$ 495	$ 461	$ 491	$ 263	$ 414	$ 421	$ 399	$ 1,958	$ 1,496	$ 2,106
Net income:
Basic (USD per share)	$ 2.06	$ 1.97	$ 1.83	$ 1.94	$ 1.03	$ 1.62	$ 1.63	$ 1.54	$ 7.80	$ 5.84	$ 8.02
Diluted (USD per share)	$ 2.03	$ 1.95	$ 1.82	$ 1.93	$ 1.02	$ 1.61	$ 1.62	$ 1.53	$ 7.73	$ 5.78	$ 7.94